Manchester United have completed the £36m signing of Monaco forward Anthony Martial, making him the world's most expensive teenage footballer.
The fee could rise to £58m.
France Under-21 international Martial, who scored eight goals in 31 Ligue 1 games last season, signed a four-year deal with the option for a fifth year.
The 19-year-old, who had been linked with Arsenal, becomes United's third most expensive signing after Angel Di Maria (£59.7m) and Juan Mata (£37.1m).
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He was allowed to leave the France squad on Monday for a medical with Louis van Gaal's side, who have given him the number nine shirt.
Monaco signed Martial for £4.4m two years ago from Lyon, who will receive about £7.35m as a result of a sell-on clause.
Conditions that would increase the fee include Martial winning the Ballon d'Or award for the world's top footballer.
The previous world record transfer fee for a teenager was £27m, which United paid for Southampton left-back Luke Shaw last summer and Paris St-Germain spent on Roma centre-back Marquinhos in 2013.
His signing came as Premier League spending passed £850m for the first time in a transfer window.
|The most expensive teenagers in world football|
|Anthony Martial||September 2015||Monaco||Manchester United||£36m (rising to £58m)|
|Luke Shaw||June 2014||Southampton||Manchester United||£27m (rising to £31m)|
|Marquinhos||July 2013||Roma||Paris St-Germain||£27m|
|Anderson||July 2007||Porto||Manchester United||£26m|
|Wayne Rooney||August 2004||Everton||Manchester United||£20m (rising to £27m)|
|All figures are reported|
'The biggest club in the world'
"I am so excited to be joining Manchester United," said Martial. "I have always wanted to play in the Premier League and to join the biggest club in the world is what every young footballer dreams of.
"I am looking forward to meeting my new team-mates and working with Louis van Gaal, who has achieved so much in his career."
Manager Van Gaal said: "Anthony is a naturally talented, young, multi-functional forward with great potential. We have been watching him for a while now and he has developed immensely during his time at Monaco.
"He has all the attributes to become a top football player; however we need to give him time to adjust to his new environment and the rhythm of the Premier League."
Monaco vice-president Vadim Vasilyev said: "We wished to keep him this season but Manchester United made an incredible offer that neither Anthony, nor AS Monaco, could refuse."
|Valencia coach Phil Neville came up against Martial in the Champions League qualifiers|
|"Of the two games and video footage I witnessed of him, he is a top, top striker. He is quick, he is strong and likes to drift out to the left. Every time he got the ball, I thought, no, get the ball away from him. He looks so dangerous and so direct.|
|"He is perfectly suited for the Premier League. I think it is a very good signing. It is a lot of money. Everybody in Spain can't believe the amount spent in England. They can't stop laughing at the fees we pay."|
|Ex-Manchester United player Neville was speaking on BBC Football Focus|
What's the reaction to the deal?
In France, it is fair to say people are a little surprised.
"Is he worth that amount of money? If you ask the people back in France, they will say no he's not," said football journalist Philippe Auclair, speaking to BBC Radio 5 live's Monday Night Club.
"This amount of money leaves people speechless in France."
Such scepticism is greeted philosophically by the powerbrokers at Old Trafford.
In the final three weeks of the transfer window, a significant shift was noted in the prices being demanded for young players.
The acceleration was so quick a United source has said they expect the 200m euros (£150m) transfer barrier to be broken within three years.
With interest expected from all of Europe's leading clubs next summer, United felt they had to make a move Monaco could not refuse.
The add-ons merely underline the high expectations that surround Martial. "If he wins the Ballon D'Or, we won't care about the money," said the source.
Who is Martial?
A France Under-21 international who has just been called up to the senior national team for the first time.
He scored 32 goals in 21 games at youth level for Lyon before breaking into the first team in the 2012-13 season, making three appearances before joining Monaco.
Martial scored two goals in 15 games in his first season at Monaco and 11 in 42 in all competitions last season.
With nine goals, he is the top teenage scorer in Europe's top five leagues since the start of 2014-15.
In a July 2015 study by the Soccerex 20 Football Value Index, Martial was ranked the 17th most valuable under-21 player in Europe at £11.6m.
Raheem Sterling, who joined Manchester City from Liverpool for a fee that could reach £49m, was rated the most valuable.
How good is he?
He has already caught the eye of France boss Didier Deschamps and clearly United think he is worth the money, but it is all about potential.
"He plays centrally, but often drifts into wide positions, more on the left than the right," said Deschamps.
"He's got a good combination of pace and power.
"He's a young player obviously, but he's got an interesting profile in an area where it's not easy to find players with both strength and speed."
He has been likened to countryman Thierry Henry, the Arsenal legend and Barcelona star who helped France win the 1998 World Cup.
Like Henry, Martial can play as a striker but also on the wings.
"The one comparison made by everybody in France - and will probably be made by everybody in England over the next few days - is he reminds people of Henry," said Auclair.
"He's not as tall - he's about two inches shorter - but he is lightning quick.
"He's got good technique, good skills, he's a good finisher, but he is still a raw product. We don't know how far he can go."