[html] How to semantically add heading to a list

a <div> is a logical division in your content, semantically this would be my first choice if I wanted to group the heading with the list:

<div class="mydiv">
    <h3>The heading</h3>
    <ul>
       <li>item</li>
       <li>item</li>
       <li>item</li>
    </ul>
</div>

then you can use the following css to style everything together as one unit

.mydiv{}
.mydiv h3{}
.mydiv ul{}
.mydiv ul li{}
etc...