Wilshere opted to leave Arsenal when his contract expired this month despite having been offered a new deal by the club.
"My family and a few of my friends are West Ham fans so everyone's buzzing".
The midfielder grew up supporting West Ham and while it would have presumably been a hard decision to end his 17-year association with Arsenal, moving on is what's best for his playing career.
The England worldwide put pen-to-paper with the Hammers and will fly out to Switzerland to link up with Manuel Pellegrini's squad at their pre-season training camp in Bad Ragaz.
Wilshere - scorer of 14 goals in his 197 appearances for the Gunners and who won two FA Cup winners medals in 2014 and 2015 - said it was well known the strong emotional ties he had with West Ham.More news: Stormy Daniels arrested at OH strip club, cancels show
"The fans, of course - everyone knows how big West Ham's fanbase is - and especially in this new stadium".
"Most importantly, he is hungry to play for West Ham, and determined to reproduce the level of performance that he has shown in the past".
"He makes me think of Mbappe because I played him at 17 years of age as he was an exceptional talent".
He becomes the latest recruit in what looks set to be a significant summer of investment for West Ham and new manager Manuel Pellegrini.
Wilshere has been capped 34 times by England but was left out of Gareth Southgate's squad for this summer's World Cup after being part of the side in Brazil four years ago.
West Ham have also been strongly linked with Borussia Dortmund winger Andriy Yarmolenko, with the Ukraine worldwide reportedly travelling to Switzerland to undergo a medical after a fee was agreed between the clubs.