"We are delighted to announce the return of Gareth Bale to the club on a season-long loan from Real Madrid," Tottenham said in a statement.
Tottenham's first game after the international break next month is away to Burnley on 24 October.
The former Southampton winger made just two appearances for Madrid after football's return from the break caused by the coronavirus pandemic and did not even travel for Madrid's Champions League exit to Manchester City in June.
Bale twice won Premier League Players' Player of the Year during his first spell at the side, which saw him score 56 goals in 203 appearances and lure Madrid into paying a record-breaking price for his services.
Spurs are badly in need of a lift after failing to qualify for the Champions League for the first time in five years last season and starting their new Premier League campaign with a dispiriting 1-0 home defeat to Everton.
Madrid, though, will reportedly retain a buy-back option on the 23-year-old for the next two seasons.