Sue Bird signed off her Olympic career with a fifth gold medal as Team USA landed a seventh successive women's basketball title, scuppering the hopes of hosts Japan in the final.

At the age of 40, Bird has declared Tokyo 2020 will be her final Games, and she helped the latest incarnation of the mighty United States team to a 90-75 win in the Saitama Super Arena.

Brittney Griner set a new USA record of 30 points in a women's Olympic final, while Diana Taurasi joined Bird in landing a fifth gold, the two longest-serving members of the team each finishing the game with seven points. Taurasi, 39, could yet play on until the 2024 Olympics in Paris.

A'ja Wilson scored 19 points on 8-of-13 shooting from the field in Sunday's final, while Breanna Stewart added 14 points and grabbed 14 rebounds.

Maki Takada led Japan with 17 points. Her team-mate Nako Motohashi drained four of five three-point shots but was far less clinical when nearer the net.

Japan made just 36 per cent of their field-goal attempts (28 of 77) and the 54 per cent success rate of the US team (37 of 69) proved a decisive factor.

The home team never led and trailed 50-39 at half-time, then 75-56 after the third quarter, and by that point the contest was all but over.

Taurasi said of her fifth gold: "It's 20 years of sacrifice, of putting everything aside and just wanting to win. It's never easy playing on this team [with] the pressure, but this group found a way to win and I'm just happy this group got to enjoy it."

Griner, who was also on the Rio 2016 team, recalled the efforts of the triumphant teams of years gone by, with this winning streak having begun at the 1996 Atlanta Games.

"Seven in a row, I mean that's just amazing. That just goes to show everything USA basketball's about," Griner said.

"Japan's hard to guard. They can shoot it anywhere on the court. They're a tough guard, they're a really good team. I'm just glad we've got this gold."