You should exec:
dnf install gcc-c++
The package you're looking for is confusingly named gcc-c++.
I had the same problem. At least I could solve it with this:
sudo yum install gcc gcc-c++
Hope it solves your problem too.
Since Fedora 22 yum has been deprecated so the commands given in other answers will actually fire up 'Dandified yum' i.e. dnf. So the new command to install g++ in recent distributions is
su -c "dnf install gcc-c++"
As of Nov 2015 this installs the 5.1.1 version.
Also note that in Fedora 23 when I gave the command g++ -v, Fedora automatically asked me if I want to install gcc-c++ package. I think thats nice.(After the install it also ran the command g++ -v for me)
Only nit pick that I can do about it is that instead of a progress indicator you just get * Downloading packages... message which you may not like if you are on a slow internet connection.
In the newer distribution you can just type command as blow
su root
dnf update
dnf install gcc-c++
instead of g++ you have to write gcc-c++
sudo dnf install gcc-c++
Run the command bellow in a terminal emulator:
sudo dnf install gcc-c++
Enter password and that's it...
Just make a sample 'Hello World' Program and try to compile it using "g++ sam.cpp" in terminal, and it will ask you if you wish to download the g++ package. Press y to install.
try
sudo dnf update and then
sudo dnf install gcc-c++
Source: Stackoverflow.com