Ronda Rousey -- I'm Officially An S.I. Cover Girl!! ... And I've Got Some Company

Ronda Rousey has officially been named as one of the girls to grace this year's Sports Illustrated Swimsuit Edition ... and she'll be joined by two others.

Nick Cannon made the announcement at a ceremony in NYC Saturday, the magazine's doing 3 different covers this year ... with Rousey, Hailey Clauson and Ashley Graham. The official announcement will be made on TV Saturday night.

You'll remember ... TMZ Sports obtained a series of photos of Rousey in the Caribbean with a painted-on suit back in January and the cover buzz began.

Chalk that up as W for Ronda.

Sports Illustrated revealed the cover last night.