What is the lightest UFC weight division?

Heavyweight 265 lbs -207 lbs

Light Heavyweight 205-187

Middleweight 185-172

Welterweight 170-157

Lightweight 155

For a regular fight you are able to weigh in one pound over the limit ex) 171 lbs for a welterweight fight. However, you must make the weight limit if you are fighting for a championship belt at any weight.