The deal is only behind deals for Philippe Coutinho, Neymar, Ousmane Dembele and Kylian Mbappe in terms of lucrativeness.
The Portuguese teenager also becomes the second most expensive teenager of all time after French star Mbappe, who moved from Monaco to PSG for a fee of €180 million.
Felix, who turned 19 in November last year, enjoyed a stellar debut season that saw him score 15 goals for Benfica and become the first teenager ever to net a Europa League hat-trick.
With Antoine Griezmann leaving Atletico this summer, the Spanish club was in the hunt for a high profile forward to lead next season’s attack.
Felix was amongst the top scorers in Portugal’s Primeira Liga last year. While he plays primarily as a striker, his versatility has also seen him selected on the wing and as an attacking midfielder.
He made his international debut in Portugal’s Nations League clash with Switzerland earlier this year, and comparisons have already been drawn between Felix and countryman Cristiano Ronaldo.