The 32-year-old bids farewell to the Gunners for a second time, having originally spent four years in North London from 2009 to 2013 before transferring to French outfit Montpellier HSC.
Beattie subsequently spent four years on the books with Manchester City before returning to Arsenal in 2019, and she departs with a total of eight major trophies to show from her two spells in the capital.
The former Scotland international won seven of those honours in her first spell at the club - including four Women's Super League titles - before clinching her most recent prize in the 2022-23 Women's League Cup.
Not long after rejoining Arsenal, Beattie was diagnosed with breast cancer in October 2020 but continued to represent her club and country, winning the Helen Rollason Award at the 2021 BBC Sports Personality of the Year Awards for "outstanding achievement in the face of adversity".
"Jen has had a beautiful career with Arsenal and we want to say a big thank you for her many years with us," Arsenal sporting director Edu told the club's official website. "She has helped to bring titles to our club and as a person, she is a great example of strength. We wish her success and happiness in the USA and she is welcome here in her home at any time."
Director of Women's Football Clare Wheatley added: "Jen leaves Arsenal with the respect and admiration of every one of us. She has been a wonderful player for us across two periods here and we're excited to watch her in this new chapter. It's a sad moment to say goodbye to such an important Arsenal figure, but Jen will always be part of this family and we look forward to seeing her soon."
Beattie struggled to force her way into Jonas Eidevall's lineup for most of the 2022-23 season, but she stepped in to deputise for the injured Leah Williamson during the final few weeks of the campaign after the Gunners captain tore her anterior cruciate ligament.
During the second leg of Arsenal's Champions League semi-final with Wolfsburg at the Emirates, Beattie forced extra time with a 75th-minute equaliser, although the Gunners suffered late heartache as they lost 3-2 after 120 minutes to fall to a 5-4 aggregate defeat.
"Gooners, I want to start by saying thank you. I don't think there was ever going to be a right time to leave Arsenal because it was never going to be an easy decision. I've had so many conflicting emotions. When I think of Arsenal, I think of home, and I think of family, and that's because of all of you," Beattie said in an open letter to Arsenal fans.
"Arsenal is the club that as an 18-year-old kid from Glasgow, gave me the opportunity of a lifetime to play with legends and to be coached by some of the most experienced in the game. And when I re-joined the club for the second time, I had that same feeling all over again when I saw the Arsenal crest at the entrance of the training ground.
"It's been an absolute privilege to represent this club. As someone who grew up watching Thierry Henry, Rachel Yankey, Dennis Bergkamp, Jayne Ludlow and Kelly Smith, I feel so lucky to be able to call myself a Gunner and to have been made so welcome from day one.
"The sheer scale of this club is never lost on me. I've always appreciated how much of an impact it's had on the community, on me and everyone involved, even my friends and family. They're now Arsenal fans too, because once you're in, you're in. Arsenal is a family like that.
"This might be the end of my journey as an Arsenal player, but as of today, I'm now a fan. I genuinely can't wait to come back to Emirates Stadium and support the team. It's the most talented group of people I've ever been a part of and I've no doubt that they'll go on to achieve whatever they want to. They've got the group to do it."
Across her two spells in North London, Beattie recorded 33 goals in 166 matches for Arsenal, and she has signed a contract with Bay FC until 2025 with the option of a further year.