The Sky Bet League Two side have announced that Bird, who left Cambridge at the end of last season, has penned a two-year deal at Huish Park.
The 27-year-old forward started out at Burnham FC, where he scored 114 goals in almost 300 games, before joining Portsmouth in 2013 and then having spells at Havant & Waterlooville, the U’s and Hartlepool.
Yeovil manager Paul Sturrock told the club’s website: “Ryan has come out of non-league at a relatively late age. If you look at his goals-to-games ratio that he has started it shows he has plenty to offer.
“I have watched him over the past few days during training and he certainly has goals in him. And goal scorers are invaluable at any football club.
“He is a big lad and will give us a great option up front. We are pleased with the signing and I hope Ryan pushes himself to be a starter in the team.”