Updated list as of Android 5.1:
af_ [Afrikaans]
af_NA [Afrikaans (Namibia)]
af_ZA [Afrikaans (South Africa)]
agq_ [Aghem]
agq_CM [Aghem (Cameroon)]
ak_ [Akan]
ak_GH [Akan (Ghana)]
am_ [Amharic]
am_ET [Amharic (Ethiopia)]
ar_ [Arabic]
ar_001 [Arabic (World)]
ar_AE [Arabic (United Arab Emirates)]
ar_BH [Arabic (Bahrain)]
ar_DJ [Arabic (Djibouti)]
ar_DZ [Arabic (Algeria)]
ar_EG [Arabic (Egypt)]
ar_EH [Arabic (Western Sahara)]
ar_ER [Arabic (Eritrea)]
ar_IL [Arabic (Israel)]
ar_IQ [Arabic (Iraq)]
ar_JO [Arabic (Jordan)]
ar_KM [Arabic (Comoros)]
ar_KW [Arabic (Kuwait)]
ar_LB [Arabic (Lebanon)]
ar_LY [Arabic (Libya)]
ar_MA [Arabic (Morocco)]
ar_MR [Arabic (Mauritania)]
ar_OM [Arabic (Oman)]
ar_PS [Arabic (Palestine)]
ar_QA [Arabic (Qatar)]
ar_SA [Arabic (Saudi Arabia)]
ar_SD [Arabic (Sudan)]
ar_SO [Arabic (Somalia)]
ar_SS [Arabic (South Sudan)]
ar_SY [Arabic (Syria)]
ar_TD [Arabic (Chad)]
ar_TN [Arabic (Tunisia)]
ar_YE [Arabic (Yemen)]
as_ [Assamese]
as_IN [Assamese (India)]
asa_ [Asu]
asa_TZ [Asu (Tanzania)]
az_ [Azerbaijani]
az_ [Azerbaijani (Cyrillic)]
az_AZ [Azerbaijani (Cyrillic,Azerbaijan)]
az_ [Azerbaijani (Latin)]
az_AZ [Azerbaijani (Latin,Azerbaijan)]
bas_ [Basaa]
bas_CM [Basaa (Cameroon)]
be_ [Belarusian]
be_BY [Belarusian (Belarus)]
bem_ [Bemba]
bem_ZM [Bemba (Zambia)]
bez_ [Bena]
bez_TZ [Bena (Tanzania)]
bg_ [Bulgarian]
bg_BG [Bulgarian (Bulgaria)]
bm_ [Bambara]
bm_ML [Bambara (Mali)]
bn_ [Bengali]
bn_BD [Bengali (Bangladesh)]
bn_IN [Bengali (India)]
bo_ [Tibetan]
bo_CN [Tibetan (China)]
bo_IN [Tibetan (India)]
br_ [Breton]
br_FR [Breton (France)]
brx_ [Bodo]
brx_IN [Bodo (India)]
bs_ [Bosnian]
bs_ [Bosnian (Cyrillic)]
bs_BA [Bosnian (Cyrillic,Bosnia and Herzegovina)]
bs_ [Bosnian (Latin)]
bs_BA [Bosnian (Latin,Bosnia and Herzegovina)]
ca_ [Catalan]
ca_AD [Catalan (Andorra)]
ca_ES [Catalan (Spain)]
ca_FR [Catalan (France)]
ca_IT [Catalan (Italy)]
cgg_ [Chiga]
cgg_UG [Chiga (Uganda)]
chr_ [Cherokee]
chr_US [Cherokee (United States)]
cs_ [Czech]
cs_CZ [Czech (Czech Republic)]
cy_ [Welsh]
cy_GB [Welsh (United Kingdom)]
da_ [Danish]
da_DK [Danish (Denmark)]
da_GL [Danish (Greenland)]
dav_ [Taita]
dav_KE [Taita (Kenya)]
de_ [German]
de_AT [German (Austria)]
de_BE [German (Belgium)]
de_CH [German (Switzerland)]
de_DE [German (Germany)]
de_LI [German (Liechtenstein)]
de_LU [German (Luxembourg)]
dje_ [Zarma]
dje_NE [Zarma (Niger)]
dua_ [Duala]
dua_CM [Duala (Cameroon)]
dyo_ [Jola-Fonyi]
dyo_SN [Jola-Fonyi (Senegal)]
dz_ [Dzongkha]
dz_BT [Dzongkha (Bhutan)]
ebu_ [Embu]
ebu_KE [Embu (Kenya)]
ee_ [Ewe]
ee_GH [Ewe (Ghana)]
ee_TG [Ewe (Togo)]
el_ [Greek]
el_CY [Greek (Cyprus)]
el_GR [Greek (Greece)]
en_ [English]
en_001 [English (World)]
en_150 [English (Europe)]
en_AG [English (Antigua and Barbuda)]
en_AI [English (Anguilla)]
en_AS [English (American Samoa)]
en_AU [English (Australia)]
en_BB [English (Barbados)]
en_BE [English (Belgium)]
en_BM [English (Bermuda)]
en_BS [English (Bahamas)]
en_BW [English (Botswana)]
en_BZ [English (Belize)]
en_CA [English (Canada)]
en_CC [English (Cocos (Keeling) Islands)]
en_CK [English (Cook Islands)]
en_CM [English (Cameroon)]
en_CX [English (Christmas Island)]
en_DG [English (Diego Garcia)]
en_DM [English (Dominica)]
en_ER [English (Eritrea)]
en_FJ [English (Fiji)]
en_FK [English (Falkland Islands (Islas Malvinas))]
en_FM [English (Micronesia)]
en_GB [English (United Kingdom)]
en_GD [English (Grenada)]
en_GG [English (Guernsey)]
en_GH [English (Ghana)]
en_GI [English (Gibraltar)]
en_GM [English (Gambia)]
en_GU [English (Guam)]
en_GY [English (Guyana)]
en_HK [English (Hong Kong)]
en_IE [English (Ireland)]
en_IM [English (Isle of Man)]
en_IN [English (India)]
en_IO [English (British Indian Ocean Territory)]
en_JE [English (Jersey)]
en_JM [English (Jamaica)]
en_KE [English (Kenya)]
en_KI [English (Kiribati)]
en_KN [English (Saint Kitts and Nevis)]
en_KY [English (Cayman Islands)]
en_LC [English (Saint Lucia)]
en_LR [English (Liberia)]
en_LS [English (Lesotho)]
en_MG [English (Madagascar)]
en_MH [English (Marshall Islands)]
en_MO [English (Macau)]
en_MP [English (Northern Mariana Islands)]
en_MS [English (Montserrat)]
en_MT [English (Malta)]
en_MU [English (Mauritius)]
en_MW [English (Malawi)]
en_NA [English (Namibia)]
en_NF [English (Norfolk Island)]
en_NG [English (Nigeria)]
en_NR [English (Nauru)]
en_NU [English (Niue)]
en_NZ [English (New Zealand)]
en_PG [English (Papua New Guinea)]
en_PH [English (Philippines)]
en_PK [English (Pakistan)]
en_PN [English (Pitcairn Islands)]
en_PR [English (Puerto Rico)]
en_PW [English (Palau)]
en_RW [English (Rwanda)]
en_SB [English (Solomon Islands)]
en_SC [English (Seychelles)]
en_SD [English (Sudan)]
en_SG [English (Singapore)]
en_SH [English (Saint Helena)]
en_SL [English (Sierra Leone)]
en_SS [English (South Sudan)]
en_SX [English (Sint Maarten)]
en_SZ [English (Swaziland)]
en_TC [English (Turks and Caicos Islands)]
en_TK [English (Tokelau)]
en_TO [English (Tonga)]
en_TT [English (Trinidad and Tobago)]
en_TV [English (Tuvalu)]
en_TZ [English (Tanzania)]
en_UG [English (Uganda)]
en_UM [English (U.S. Outlying Islands)]
en_US [English (United States)]
en_US [English (United States,Computer)]
en_VC [English (St. Vincent & Grenadines)]
en_VG [English (British Virgin Islands)]
en_VI [English (U.S. Virgin Islands)]
en_VU [English (Vanuatu)]
en_WS [English (Samoa)]
en_ZA [English (South Africa)]
en_ZM [English (Zambia)]
en_ZW [English (Zimbabwe)]
eo_ [Esperanto]
es_ [Spanish]
es_419 [Spanish (Latin America)]
es_AR [Spanish (Argentina)]
es_BO [Spanish (Bolivia)]
es_CL [Spanish (Chile)]
es_CO [Spanish (Colombia)]
es_CR [Spanish (Costa Rica)]
es_CU [Spanish (Cuba)]
es_DO [Spanish (Dominican Republic)]
es_EA [Spanish (Ceuta and Melilla)]
es_EC [Spanish (Ecuador)]
es_ES [Spanish (Spain)]
es_GQ [Spanish (Equatorial Guinea)]
es_GT [Spanish (Guatemala)]
es_HN [Spanish (Honduras)]
es_IC [Spanish (Canary Islands)]
es_MX [Spanish (Mexico)]
es_NI [Spanish (Nicaragua)]
es_PA [Spanish (Panama)]
es_PE [Spanish (Peru)]
es_PH [Spanish (Philippines)]
es_PR [Spanish (Puerto Rico)]
es_PY [Spanish (Paraguay)]
es_SV [Spanish (El Salvador)]
es_US [Spanish (United States)]
es_UY [Spanish (Uruguay)]
es_VE [Spanish (Venezuela)]
et_ [Estonian]
et_EE [Estonian (Estonia)]
eu_ [Basque]
eu_ES [Basque (Spain)]
ewo_ [Ewondo]
ewo_CM [Ewondo (Cameroon)]
fa_ [Persian]
fa_AF [Persian (Afghanistan)]
fa_IR [Persian (Iran)]
ff_ [Fulah]
ff_SN [Fulah (Senegal)]
fi_ [Finnish]
fi_FI [Finnish (Finland)]
fil_ [Filipino]
fil_PH [Filipino (Philippines)]
fo_ [Faroese]
fo_FO [Faroese (Faroe Islands)]
fr_ [French]
fr_BE [French (Belgium)]
fr_BF [French (Burkina Faso)]
fr_BI [French (Burundi)]
fr_BJ [French (Benin)]
fr_BL [French (Saint Barthélemy)]
fr_CA [French (Canada)]
fr_CD [French (Congo (DRC))]
fr_CF [French (Central African Republic)]
fr_CG [French (Congo (Republic))]
fr_CH [French (Switzerland)]
fr_CI [French (Côte d’Ivoire)]
fr_CM [French (Cameroon)]
fr_DJ [French (Djibouti)]
fr_DZ [French (Algeria)]
fr_FR [French (France)]
fr_GA [French (Gabon)]
fr_GF [French (French Guiana)]
fr_GN [French (Guinea)]
fr_GP [French (Guadeloupe)]
fr_GQ [French (Equatorial Guinea)]
fr_HT [French (Haiti)]
fr_KM [French (Comoros)]
fr_LU [French (Luxembourg)]
fr_MA [French (Morocco)]
fr_MC [French (Monaco)]
fr_MF [French (Saint Martin)]
fr_MG [French (Madagascar)]
fr_ML [French (Mali)]
fr_MQ [French (Martinique)]
fr_MR [French (Mauritania)]
fr_MU [French (Mauritius)]
fr_NC [French (New Caledonia)]
fr_NE [French (Niger)]
fr_PF [French (French Polynesia)]
fr_PM [French (Saint Pierre and Miquelon)]
fr_RE [French (Réunion)]
fr_RW [French (Rwanda)]
fr_SC [French (Seychelles)]
fr_SN [French (Senegal)]
fr_SY [French (Syria)]
fr_TD [French (Chad)]
fr_TG [French (Togo)]
fr_TN [French (Tunisia)]
fr_VU [French (Vanuatu)]
fr_WF [French (Wallis and Futuna)]
fr_YT [French (Mayotte)]
ga_ [Irish]
ga_IE [Irish (Ireland)]
gl_ [Galician]
gl_ES [Galician (Spain)]
gsw_ [Swiss German]
gsw_CH [Swiss German (Switzerland)]
gsw_LI [Swiss German (Liechtenstein)]
gu_ [Gujarati]
gu_IN [Gujarati (India)]
guz_ [Gusii]
guz_KE [Gusii (Kenya)]
gv_ [Manx]
gv_IM [Manx (Isle of Man)]
ha_ [Hausa]
ha_ [Hausa (Latin)]
ha_GH [Hausa (Latin,Ghana)]
ha_NE [Hausa (Latin,Niger)]
ha_NG [Hausa (Latin,Nigeria)]
haw_ [Hawaiian]
haw_US [Hawaiian (United States)]
iw_ [Hebrew]
iw_IL [Hebrew (Israel)]
hi_ [Hindi]
hi_IN [Hindi (India)]
hr_ [Croatian]
hr_BA [Croatian (Bosnia and Herzegovina)]
hr_HR [Croatian (Croatia)]
hu_ [Hungarian]
hu_HU [Hungarian (Hungary)]
hy_ [Armenian]
hy_AM [Armenian (Armenia)]
in_ [Indonesian]
in_ID [Indonesian (Indonesia)]
ig_ [Igbo]
ig_NG [Igbo (Nigeria)]
ii_ [Sichuan Yi]
ii_CN [Sichuan Yi (China)]
is_ [Icelandic]
is_IS [Icelandic (Iceland)]
it_ [Italian]
it_CH [Italian (Switzerland)]
it_IT [Italian (Italy)]
it_SM [Italian (San Marino)]
ja_ [Japanese]
ja_JP [Japanese (Japan)]
jgo_ [Ngomba]
jgo_CM [Ngomba (Cameroon)]
jmc_ [Machame]
jmc_TZ [Machame (Tanzania)]
ka_ [Georgian]
ka_GE [Georgian (Georgia)]
kab_ [Kabyle]
kab_DZ [Kabyle (Algeria)]
kam_ [Kamba]
kam_KE [Kamba (Kenya)]
kde_ [Makonde]
kde_TZ [Makonde (Tanzania)]
kea_ [Kabuverdianu]
kea_CV [Kabuverdianu (Cape Verde)]
khq_ [Koyra Chiini]
khq_ML [Koyra Chiini (Mali)]
ki_ [Kikuyu]
ki_KE [Kikuyu (Kenya)]
kk_ [Kazakh]
kk_ [Kazakh (Cyrillic)]
kk_KZ [Kazakh (Cyrillic,Kazakhstan)]
kkj_ [Kako]
kkj_CM [Kako (Cameroon)]
kl_ [Kalaallisut]
kl_GL [Kalaallisut (Greenland)]
kln_ [Kalenjin]
kln_KE [Kalenjin (Kenya)]
km_ [Khmer]
km_KH [Khmer (Cambodia)]
kn_ [Kannada]
kn_IN [Kannada (India)]
ko_ [Korean]
ko_KP [Korean (North Korea)]
ko_KR [Korean (South Korea)]
kok_ [Konkani]
kok_IN [Konkani (India)]
ks_ [Kashmiri]
ks_ [Kashmiri (Arabic)]
ks_IN [Kashmiri (Arabic,India)]
ksb_ [Shambala]
ksb_TZ [Shambala (Tanzania)]
ksf_ [Bafia]
ksf_CM [Bafia (Cameroon)]
kw_ [Cornish]
kw_GB [Cornish (United Kingdom)]
ky_ [Kyrgyz]
ky_ [Kyrgyz (Cyrillic)]
ky_KG [Kyrgyz (Cyrillic,Kyrgyzstan)]
lag_ [Langi]
lag_TZ [Langi (Tanzania)]
lg_ [Ganda]
lg_UG [Ganda (Uganda)]
lkt_ [Lakota]
lkt_US [Lakota (United States)]
ln_ [Lingala]
ln_AO [Lingala (Angola)]
ln_CD [Lingala (Congo (DRC))]
ln_CF [Lingala (Central African Republic)]
ln_CG [Lingala (Congo (Republic))]
lo_ [Lao]
lo_LA [Lao (Laos)]
lt_ [Lithuanian]
lt_LT [Lithuanian (Lithuania)]
lu_ [Luba-Katanga]
lu_CD [Luba-Katanga (Congo (DRC))]
luo_ [Luo]
luo_KE [Luo (Kenya)]
luy_ [Luyia]
luy_KE [Luyia (Kenya)]
lv_ [Latvian]
lv_LV [Latvian (Latvia)]
mas_ [Masai]
mas_KE [Masai (Kenya)]
mas_TZ [Masai (Tanzania)]
mer_ [Meru]
mer_KE [Meru (Kenya)]
mfe_ [Morisyen]
mfe_MU [Morisyen (Mauritius)]
mg_ [Malagasy]
mg_MG [Malagasy (Madagascar)]
mgh_ [Makhuwa-Meetto]
mgh_MZ [Makhuwa-Meetto (Mozambique)]
mgo_ [Meta']
mgo_CM [Meta' (Cameroon)]
mk_ [Macedonian]
mk_MK [Macedonian (Macedonia (FYROM))]
ml_ [Malayalam]
ml_IN [Malayalam (India)]
mn_ [Mongolian]
mn_ [Mongolian (Cyrillic)]
mn_MN [Mongolian (Cyrillic,Mongolia)]
mr_ [Marathi]
mr_IN [Marathi (India)]
ms_ [Malay]
ms_ [Malay (Latin)]
ms_BN [Malay (Latin,Brunei)]
ms_MY [Malay (Latin,Malaysia)]
ms_SG [Malay (Latin,Singapore)]
mt_ [Maltese]
mt_MT [Maltese (Malta)]
mua_ [Mundang]
mua_CM [Mundang (Cameroon)]
my_ [Burmese]
my_MM [Burmese (Myanmar (Burma))]
naq_ [Nama]
naq_NA [Nama (Namibia)]
nb_ [Norwegian Bokmål]
nb_NO [Norwegian Bokmål (Norway)]
nb_SJ [Norwegian Bokmål (Svalbard and Jan Mayen)]
nd_ [North Ndebele]
nd_ZW [North Ndebele (Zimbabwe)]
ne_ [Nepali]
ne_IN [Nepali (India)]
ne_NP [Nepali (Nepal)]
nl_ [Dutch]
nl_AW [Dutch (Aruba)]
nl_BE [Dutch (Belgium)]
nl_BQ [Dutch (Caribbean Netherlands)]
nl_CW [Dutch (Curaçao)]
nl_NL [Dutch (Netherlands)]
nl_SR [Dutch (Suriname)]
nl_SX [Dutch (Sint Maarten)]
nmg_ [Kwasio]
nmg_CM [Kwasio (Cameroon)]
nn_ [Norwegian Nynorsk]
nn_NO [Norwegian Nynorsk (Norway)]
nnh_ [Ngiemboon]
nnh_CM [Ngiemboon (Cameroon)]
nus_ [Nuer]
nus_SD [Nuer (Sudan)]
nyn_ [Nyankole]
nyn_UG [Nyankole (Uganda)]
om_ [Oromo]
om_ET [Oromo (Ethiopia)]
om_KE [Oromo (Kenya)]
or_ [Oriya]
or_IN [Oriya (India)]
pa_ [Punjabi]
pa_ [Punjabi (Arabic)]
pa_PK [Punjabi (Arabic,Pakistan)]
pa_ [Punjabi (Gurmukhi)]
pa_IN [Punjabi (Gurmukhi,India)]
pl_ [Polish]
pl_PL [Polish (Poland)]
ps_ [Pashto]
ps_AF [Pashto (Afghanistan)]
pt_ [Portuguese]
pt_AO [Portuguese (Angola)]
pt_BR [Portuguese (Brazil)]
pt_CV [Portuguese (Cape Verde)]
pt_GW [Portuguese (Guinea-Bissau)]
pt_MO [Portuguese (Macau)]
pt_MZ [Portuguese (Mozambique)]
pt_PT [Portuguese (Portugal)]
pt_ST [Portuguese (São Tomé and Príncipe)]
pt_TL [Portuguese (Timor-Leste)]
rm_ [Romansh]
rm_CH [Romansh (Switzerland)]
rn_ [Rundi]
rn_BI [Rundi (Burundi)]
ro_ [Romanian]
ro_MD [Romanian (Moldova)]
ro_RO [Romanian (Romania)]
rof_ [Rombo]
rof_TZ [Rombo (Tanzania)]
ru_ [Russian]
ru_BY [Russian (Belarus)]
ru_KG [Russian (Kyrgyzstan)]
ru_KZ [Russian (Kazakhstan)]
ru_MD [Russian (Moldova)]
ru_RU [Russian (Russia)]
ru_UA [Russian (Ukraine)]
rw_ [Kinyarwanda]
rw_RW [Kinyarwanda (Rwanda)]
rwk_ [Rwa]
rwk_TZ [Rwa (Tanzania)]
saq_ [Samburu]
saq_KE [Samburu (Kenya)]
sbp_ [Sangu]
sbp_TZ [Sangu (Tanzania)]
seh_ [Sena]
seh_MZ [Sena (Mozambique)]
ses_ [Koyraboro Senni]
ses_ML [Koyraboro Senni (Mali)]
sg_ [Sango]
sg_CF [Sango (Central African Republic)]
shi_ [Tachelhit]
shi_ [Tachelhit (Latin)]
shi_MA [Tachelhit (Latin,Morocco)]
shi_ [Tachelhit (Tifinagh)]
shi_MA [Tachelhit (Tifinagh,Morocco)]
si_ [Sinhala]
si_LK [Sinhala (Sri Lanka)]
sk_ [Slovak]
sk_SK [Slovak (Slovakia)]
sl_ [Slovenian]
sl_SI [Slovenian (Slovenia)]
sn_ [Shona]
sn_ZW [Shona (Zimbabwe)]
so_ [Somali]
so_DJ [Somali (Djibouti)]
so_ET [Somali (Ethiopia)]
so_KE [Somali (Kenya)]
so_SO [Somali (Somalia)]
sq_ [Albanian]
sq_AL [Albanian (Albania)]
sq_MK [Albanian (Macedonia (FYROM))]
sq_XK [Albanian (Kosovo)]
sr_ [Serbian]
sr_ [Serbian (Cyrillic)]
sr_BA [Serbian (Cyrillic,Bosnia and Herzegovina)]
sr_ME [Serbian (Cyrillic,Montenegro)]
sr_RS [Serbian (Cyrillic,Serbia)]
sr_XK [Serbian (Cyrillic,Kosovo)]
sr_ [Serbian (Latin)]
sr_BA [Serbian (Latin,Bosnia and Herzegovina)]
sr_ME [Serbian (Latin,Montenegro)]
sr_RS [Serbian (Latin,Serbia)]
sr_XK [Serbian (Latin,Kosovo)]
sv_ [Swedish]
sv_AX [Swedish (Åland Islands)]
sv_FI [Swedish (Finland)]
sv_SE [Swedish (Sweden)]
sw_ [Swahili]
sw_KE [Swahili (Kenya)]
sw_TZ [Swahili (Tanzania)]
sw_UG [Swahili (Uganda)]
swc_ [Congo Swahili]
swc_CD [Congo Swahili (Congo (DRC))]
ta_ [Tamil]
ta_IN [Tamil (India)]
ta_LK [Tamil (Sri Lanka)]
ta_MY [Tamil (Malaysia)]
ta_SG [Tamil (Singapore)]
te_ [Telugu]
te_IN [Telugu (India)]
teo_ [Teso]
teo_KE [Teso (Kenya)]
teo_UG [Teso (Uganda)]
th_ [Thai]
th_TH [Thai (Thailand)]
ti_ [Tigrinya]
ti_ER [Tigrinya (Eritrea)]
ti_ET [Tigrinya (Ethiopia)]
to_ [Tongan]
to_TO [Tongan (Tonga)]
tr_ [Turkish]
tr_CY [Turkish (Cyprus)]
tr_TR [Turkish (Turkey)]
twq_ [Tasawaq]
twq_NE [Tasawaq (Niger)]
tzm_ [Central Atlas Tamazight]
tzm_ [Central Atlas Tamazight (Latin)]
tzm_MA [Central Atlas Tamazight (Latin,Morocco)]
ug_ [Uyghur]
ug_ [Uyghur (Arabic)]
ug_CN [Uyghur (Arabic,China)]
uk_ [Ukrainian]
uk_UA [Ukrainian (Ukraine)]
ur_ [Urdu]
ur_IN [Urdu (India)]
ur_PK [Urdu (Pakistan)]
uz_ [Uzbek]
uz_ [Uzbek (Arabic)]
uz_AF [Uzbek (Arabic,Afghanistan)]
uz_ [Uzbek (Cyrillic)]
uz_UZ [Uzbek (Cyrillic,Uzbekistan)]
uz_ [Uzbek (Latin)]
uz_UZ [Uzbek (Latin,Uzbekistan)]
vai_ [Vai]
vai_ [Vai (Latin)]
vai_LR [Vai (Latin,Liberia)]
vai_ [Vai (Vai)]
vai_LR [Vai (Vai,Liberia)]
vi_ [Vietnamese]
vi_VN [Vietnamese (Vietnam)]
vun_ [Vunjo]
vun_TZ [Vunjo (Tanzania)]
xog_ [Soga]
xog_UG [Soga (Uganda)]
yav_ [Yangben]
yav_CM [Yangben (Cameroon)]
yo_ [Yoruba]
yo_BJ [Yoruba (Benin)]
yo_NG [Yoruba (Nigeria)]
zgh_ [Standard Moroccan Tamazight]
zgh_MA [Standard Moroccan Tamazight (Morocco)]
zh_ [Chinese]
zh_ [Chinese (Simplified Han)]
zh_CN [Chinese (Simplified Han,China)]
zh_HK [Chinese (Simplified Han,Hong Kong)]
zh_MO [Chinese (Simplified Han,Macau)]
zh_SG [Chinese (Simplified Han,Singapore)]
zh_ [Chinese (Traditional Han)]
zh_HK [Chinese (Traditional Han,Hong Kong)]
zh_MO [Chinese (Traditional Han,Macau)]
zh_TW [Chinese (Traditional Han,Taiwan)]
zu_ [Zulu]
zu_ZA [Zulu (South Africa)]
Original Answer :
As of Android 5.0, all languages in BCP 47 are available for application development (they may not necessarily be available for selection in a given device's system settings, though). When using ISO 639-1 codes, the resource folder has the format values-xx... where xx is the ISO-639-1 code.
When using BCP 47 tags, the resource folder is named values-b+xxx... where xxx is the three-letter language code.
Here's the list for before Android 2.3 (Source)
Language / Locale Supported since version English, US (en_US) 1.1 German, Germany (de_DE) 1.1 Chinese, PRC (zh_CN) 1.5 Chinese, Taiwan (zh_TW) 1.5 Czech, Czech Republic (cs_CZ) 1.5 Dutch, Belgium (nl_BE) 1.5 Dutch, Netherlands (nl_NL) 1.5 English, Australia (en_AU) 1.5 English, Britain (en_GB) 1.5 English, Canada (en_CA) 1.5 English, New Zealand (en_NZ) 1.5 English, Singapore(en_SG) 1.5 French, Belgium (fr_BE) 1.5 French, Canada (fr_CA) 1.5 French, France (fr_FR) 1.5 French, Switzerland (fr_CH) 1.5 German, Austria (de_AT) 1.5 German, Liechtenstein (de_LI) 1.5 German, Switzerland (de_CH) 1.5 Italian, Italy (it_IT) 1.5 Italian, Switzerland (it_CH) 1.5 Japanese (ja_JP) 1.5 Korean (ko_KR) 1.5 Polish (pl_PL) 1.5 Russian (ru_RU) 1.5 Spanish (es_ES) 1.5 Arabic, Egypt (ar_EG) 2.3 Arabic, Israel (ar_IL) 2.3 Bulgarian, Bulgaria (bg_BG) 2.3 Catalan, Spain (ca_ES) 2.3 Croatian, Croatia (hr_HR) 2.3 Danish, Denmark(da_DK) 2.3 English, India (en_IN) 2.3 English, Ireland (en_IE) 2.3 English, Zimbabwe (en_ZA) 2.3 Finnish, Finland (fi_FI) 2.3 Greek, Greece (el_GR) 2.3 Hebrew, Israel (iw_IL)* 2.3 Hindi, India (hi_IN) 2.3 Hungarian, Hungary (hu_HU) 2.3 Indonesian, Indonesia (in_ID)* 2.3 Latvian, Latvia (lv_LV) 2.3 Lithuanian, Lithuania (lt_LT) 2.3 Norwegian-Bokmål, Norway(nb_NO) 2.3 Portuguese, Brazil (pt_BR) 2.3 Portuguese, Portugal (pt_PT) 2.3 Romanian, Romania (ro_RO) 2.3 Serbian (sr_RS) 2.3 Slovak, Slovakia (sk_SK) 2.3 Slovenian, Slovenia (sl_SI) 2.3 Spanish, US (es_US) 2.3 Swedish, Sweden (sv_SE) 2.3 Tagalog, Philippines (tl_PH) 2.3 Thai, Thailand (th_TH) 2.3 Turkish, Turkey (tr_TR) 2.3 Ukrainian, Ukraine (uk_UA) 2.3 Vietnamese, Vietnam (vi_VN) 2.3*Note that Java uses several deprecated two-letter codes. The Hebrew (“he”) >language code is rewritten as “iw”, Indonesian (“id”) as “in”, and Yiddish (“yi”) as “ji”. This rewriting happens even if you construct your own Locale object, not just for instances returned by the various lookup methods. See also https://issuetracker.google.com/issues/36908826.