Spurs' new number 16 returns to England and London after a previous mixed spell at Chelsea, despite winning the Champions League, the European Super Cup and the Club World Cup during that time.
The 27-year-old scored 23 goals in 89 appearances during his time at Stamford Bridge.
In August 2022, he returned to Leipzig after four consecutive seasons as the team's top scorer but has failed to hit the same heights in his second stint.
Across two spells for the German side, he has scored a total of 113 goals in 213 games.
On the international stage, Werner took part in the 2018 World Cup and the 2020 European Championships and has scored 24 goals for Germany to date.
The pacey forward has 57 senior international caps but last played for his country in a friendly defeat by Belgium in March last year.
"I'm very happy to be here," Werner told Tottenham's official website.
"I've joined a very, very big club, we have often played against each other already – it doesn't matter if I was playing for Chelsea or Leipzig, they were always big, big games to play against Spurs – and now I'm happy to be part of the team at the Club and I'm really looking forward to it.
"For me, I thought straight away that it fits perfectly. Then the stadium, to play there every game is something special and also the team, I think we have some very good players. All of it was very interesting to me.
"I hope that I can be the best player I can be here. The people who have followed me a little bit in the Premier League, know that I can bring my speed, and that I can be a threat for the opponents so that's what I want to bring to the team.
"Off the pitch, I think I can be a funny guy and I hope that I can arrive well into the team and that they are happy with me and my personality."
The north London side were openly on the lookout to bolster their attacking options in the January transfer window after captain Son Heung-min left to represent South Korea in the Asian Cup, potentially missing up to a month of action in England.
Werner also revealed his excitement at linking up with Spurs boss Ange Postecoglou and his hopes for more playing time ahead of Euro 2024, which is being held in Germany this summer.
He is expected to be available when Tottenham face Manchester United in the Premier League on Sunday, January 14th.
Spurs are currently fifth in the Premier League standings with 39 points, six behind leaders Liverpool.
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