How to remove indentation from an unordered list item?

Set the list style and left padding to nothing.

ul {
    list-style: none;
    padding-left: 0;
}​

ul {
  list-style: none;
  padding-left: 0;
}

<ul>
  <li>a</li>
  <li>b</li>
  <li>c</li>
</ul>

To maintain the bullets you can replace the list-style: none with list-style-position: inside or the shorthand list-style: inside:

ul {
  list-style-position: inside;
  padding-left: 0;
}

ul {
  list-style-position: inside;
  padding-left: 0;
}

<ul>
  <li>a</li>
  <li>b</li>
  <li>c</li>
</ul>