A nine-year-old English bulldog was named the winner of the 2018 World's Ugliest Dog contest in the San Francisco Bay Area.

Zsa Zsa won the title Saturday night at the Sonoma-Marin Sonoma-Marin Fairgrounds in Petaluma.

The dog's owner Megan Brainard of Anoka, Minnesota, will receive $US1500 ($A2015) for Zsa Zsa's win. Brainard found Zsa Zsa on a pet-finding site, according to the contest bio.

Dogs in the annual competition flaunt their imperfections - some have hairless bodies, others have lolling tongues. The dogs and their handlers walk down a red carpet. The dogs are evaluated by a panel of judges.

The contestants included a blackhead-covered Chinese Crested-Dachshund mutt, a bulldog mix with excess wrinkly skin and a Pekingese named Wild Thang.

Last year's winner was a 57-kilogram gentle giant named Martha - a Neopolitan Mastiff with gas and a droopy face.

The contest is in its 30th year. It is usually held on Friday nights, but organisers moved the competition to Saturday in an effort to draw a bigger audience.