The 23-year-old becomes Spurs’ fifth signing of the summer after Kevin Wimmer, Kieran Trippier, Toby Alderweireld and Clinton Njie.
A 44-cap South Korea international, Son has spent his whole senior career in the Bundesliga, making his name at Hamburg before joining Leverkusen in 2013.
Son emerged as one of the Bundesliga’s leading attackers at the BayArena, scoring 29 goals in 87 appearances from an advanced position, while he also scored for South Korea in last summer’s World Cup.
Son, who is adept with both feet, will wear the number 7 shirt at Spurs – who he branded as “a big club”.
“Spurs is such a big club and a really good team. My goal has always been to play in the Premier League and I have a great opportunity to do that now with Tottenham – I am really happy about this.
“I am also very pleased and honoured to work together with good players such as Harry Kane, Christian Eriksen and all the players at Spurs. I’d like to help them perform and, together with them, make our team even more successful.
“I am a player who really loves football. I learned the game under my father, who worked as a football coach in my school,” he explained. “I’ve loved the game since I was a child and formally started to play when I was 10 years old.
“I told my father that I really wanted to become a professional footballer and, because football is in my blood, I’ve always trained hard with the dream to one day play in Europe and the Premier League.
“I’ve tried hard to learn many things throughout my career so far, I’ve played many games already and gathered a lot of experience for my age. That makes me play better and score goals.
“I’m very excited to play at White Hart Lane,” he added. “I haven’t played at the stadium before but I’m looking forward to going there and performing for the Spurs fans as soon as possible. The support I get from the fans motivates me more and more.
“In the Premier League there are a lot of good players so I have to really work hard and be prepared to show my ability. I like to play a passing game and prefer to work with offensive players who are dominant and can scare the opponents. I am right footed, but I’ve trained with both feet so I can use them freely. Bold and daring – this is how I like to try to play.”