The UFC legend flew back from shooting a movie in Colombia to make a surprise (not really a surprise) appearance at the end of the Royal Rumble in Philly on Sunday night ... and the crowd went wild.

Rousey didn't participate in the 30 woman tourney -- but entered the ring after the Rumble to a wild ovation and pointed to a Wrestlemania sign. Clearly the plan is to have her in either the main event or a very prominent match during the biggest WWE event of the year in April.

As TMZ Sports previously reported, Rousey had been in talks with WWE for a while -- with Triple H flying in to meet her in California earlier this month to seal the deal.

Obviously, he got the deal done -- we're told she's a full time WWE superstar now.

Rousey told ESPN the deal is for several years -- and she passed on other opportunities that could have paid more because she realized wrestling in the WWE would make her the happiest.

"This is my life now."

GET 'EM, ROUSEY!!!