The Venezuela international arrived in England to complete a medical at the end of last week and has now rubberstamped the move by signing a four-year contract.
"I am very happy to be here," said Rondon of the move, which sees him become West Brom's fifth signing of the summer.
"This is a new opportunity in my career. I can’t wait to be with the other players and to play.
"The club showed a lot of interest in me, that’s what is important for a player, what you take into account, and there are expectations of me."
Rondon signed for Malaga in 2010 and impressed with 25 goals in 67 appearances before moving to Russia with Rubin Kazan in 2012.
The 25-year-old forward stayed there for two years before Zenit in January 2014, scoring 20 times in 37 games for the Russian champions to earn a move to The Hawthorns.
Baggies head coach Tony Pulis said of Rondon: "He’s got a fantastic goalscoring record in some of the top leagues in Europe and for his country. He’s 25 years of age and still to fulfil his full potential.
"We hope he hits the ground running of course but understand it might take him time to settle. I’m sure our fans will help him and get behind him.
"But we feel with age on his side and the prices English clubs are asking for their players, it’s a deal worth doing.
"He comes highly recommended. I have spoken to Manuel (Pellegrini) and AVB (Andre Villas-Boas), who have worked with him, and they were full of praise for the lad. We are looking forward to working with him."
