Businessman Jake Silverstein has made "a significant investment" in Swansea City, joining fellow Americans Steve Kaplan and Jason Levien on the club's board of directors.
Silverstein is a co-owner of Major League Soccer side Houston Dynamo and National Women's Soccer League Cup winners Houston Dash.
His investment has been matched with further funds from Kaplan and Levien.
"I love watching the Swans play," Silverstein told the club website.
"The team has developed such a distinctive and engaging style on the pitch, and I have a deep appreciation for its fan culture and the club's commitment to its supporters.
"By joining the club's board, it will allow me to become actively involved. It's something I am passionate about and, as such, I will be applying a lot of focus on the football club going forward.''
Talks over the deal have been taking place over the last two months, before gathering pace over the last fortnight.
The exact value of the investment is not clear, although it is thought Silverstein's place on the board means he is likely to have at least a 5% stake in the club.
At the time of the US takeover in 2016, Swansea City was valued at £100m with Kaplan and Levien taking a 68% stake.
It is understood the original investment will be in the form of a loan to the football club, providing an immediate boost to the club's finances which had been hit by relegation from the Premier League in 2018.
The club made a pre-tax loss of £7m in their most recent accounts for the period covering the 2018/19 season, despite the sales of several key players and the wage bill being halved.
Chairman Trevor Birch had warned of the potential of further cuts even before the financial hit of the coronavirus pandemic.
The loan - matched by one from Kaplan and Levien - is expected to be converted into shares at a later date, with other shareholders given the option to invest or see their shares diluted.
Swansea's Supporters Trust - who had been aware of the talks - currently has a 21.1% stake in the club.
In a statement, the Trust said it "cannot be against genuine investment in our football club", but added that it was disappointed that it had "not been informed... that any agreement had been reached" despite attending a board meeting last week on potential new funds being made available to the club.
Silverstein is the chief executive of Stormlight Holdings, his family's American-based private investment firm, and his involvement was welcomed by majority shareholders Kaplan and Levien.
"Jake is a highly-respected individual, businessman and sports team investor. He has experience, knowledge and expertise across a wide range of fields which will be an asset to Swansea City," the pair said in a joint statement.
"We are looking forward to his contribution."
Swansea reached the Championship play-offs this season, only to lose to Brentford in the two-legged semi-finals, and face a third season in the second tier after relegation from the Premier League.