Rice has penned an open letter to Hammers fans as the club confirmed their club captain was leaving – though there was no mention of ‘Arsenal’ in either statement.
The Gunners have agreed a £105million deal to sign Rice, breaking the British transfer record.
“The last few days and weeks have been an absolute whirlwind of emotion,” Rice wrote.
“You have taken me into your hearts as one of your own from day one. Even when it was just a handful of fans at the Under-18 or Under-23 games, I felt that love, and it has just grown stronger as the years have passed.
“Playing in front of you has been an honour, we have had such great times together, and you all mean so much to me.
“I want you to know how tough a decision it has been for me to leave an environment that I have loved and cherished so much.
“Ultimately, though, it has only ever been about my ambition to play at the very highest level of the game.”
Rice joined West Ham as a 14-year-old, hacing been released from Chelsea’s academy, and made his first-team debut three years later, on the last day of the 2016-17 Premier League season against Burnley.
The 24-year-old’s final game was the Europa Conference League final, which West Ham won to end a decades-long trophy drought.
“Playing on the opposite team to West Ham for the first time will be an unusual experience,” added Rice.
“I’m not sure yet exactly how I will feel, but I also know you will all understand and respect that my professional loyalties have to now lie with my new club.
“I will always give 100% every single time I pull on the shirt – because that is how I have been brought up at West Ham, and I’m sure you wouldn’t expect anything else.”