The London Lions defeated Besiktas 81-70 at a packed Copper Box Arena to win the EuroCup and become Britain's first European champions.
The Turkish side held a seven-point lead from the first leg in Istanbul and went into the final seconds with a total advantage of two points.
But Holly Winterburn's 3-pointer and Megan Gustafson's two free throws sealed the Lions' victory.
Carly Samuelson scored a game-high 19 points and was named Finals MVP.
She said, “I'm very proud of us. We didn't perform as well as we wanted in the game in Turkey, but we fought there and that fight led us to this trophy.”
“When Holly made that shot, I knew it was in my heart. We're a really close team and everyone stepped up.”
After losing the first leg 75-68 in Istanbul, the Lions needed to win the second leg by eight points to clinch the trophy.
No British team has ever reached the final of a European basketball tournament, with the men's team London Lions being knocked out in the semi-finals two weeks ago.
The Lions got off to a strong start, taking a 23-17 lead by the end of the first quarter and extending their lead to 45-35 at halftime.
But Besiktas knew that the lead was enough to clinch the trophy and pulled it back to a five-point game at 60-55 by the end of the third quarter.
However, Winterburn and Gustafsson scored in the final minutes of the game, clinching a come-from-behind victory.
“It was a battle until the last possession,” said Winterburn, 23, who will leave the club at the end of the season. “They hit some big shots at the end, but we won this one.”
“We deserve this. We've practiced hard every day. The group has come together. I don't think we'll ever play a team like this again.”
“Given the funding situation, that is not an option.” [for me] It's a shame that it will remain. I can't thank London enough for what it has done for me and British basketball. ”
Winterburn and England captain Temi Fagbenle are among the players to leave the club at the end of the season, with the Lions unlikely to qualify for next year's European competition due to lack of funds.