Martha is big, ugly, lazy and gassy. And a world champion.

In a competition annually dominated by the old, the tiny and the hairless, the three-year-old Neapolitan mastiff used her lollygagging youth to win the 29th annual World's Ugliest Dog Contest.

Martha, a three-year-old Neapolitan mastiff, won the World's Ugliest Dog Contest on Friday. Credit:AP

She was a favourite of the Northern California crowd from the start, often plopping down on her side on stage with her droopy face spread across the ground when she was supposed to be showing off.

The judges didn't even need to hear her signature snore to give her the award.