The 32-year-old midfielder has returned to Upton Park on a season-long deal and is in line to make his second debut for the Hammers against Norwich City on September 15
The Israel international first joined the Hammers in 2005 from Spanish side Racing Santander, helping the club to an FA Cup final in his first season before moving on to Liverpool and then Chelsea.
Earlier reports suggested that the two clubs had failed to agree a deal after the Blues had refused to cover part of the 32-year-old's wages, however, Benayoun took to his Twitter account on Friday to announce that an agreement had been reached, while also denying that there had been interest from both Arsenal and Liverpool.
Benayoun tweeted: "After a long and busy day I can say I had 3 offers from PL clubs..but not from liverpool or arsenal like some reports..
"But I'm very happy to confirm that I will join on loan to West Ham! Can't wait to start..great club."
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The midfielder went on to enjoy three years at Anfield with Liverpool, where he scored 18 goals in 92 appearances and became an integral part of the Reds' midfield.
Injury hampered his time at Chelsea, but he has now been handed the opportunity to re-vitalise his career at the Boleyn Ground as Sam Allardyce's men look to ensure Premier League survival.