Though it couldn't knock The Lion King of its perch at the top of the box office chart, it became the director's highest ever opening.
It beat the haul of $38.1 million for 2009's Inglorious Basterds - also starring OUATIH’s - Brad Pitt his previous box office record holder.
Forecasts had put the movie in the range of a $30 million to $40 million bow, a high bar for a movie with an R-rating.
The star-studded project, which cost $90 million to make – finds Leonardo DiCaprio and Brad Pitt as a TV actor and his stuntman navigating the choppy waters of late 60s Hollywood, encountering Margot Robbie's Sharon Tate along the way, the wife of director Roman Polanski who would be murdered by members of the Manson Family cult.
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It also stars Margaret Qualley, Timothy Olyphant, Austin Butler, Dakota Fanning, Bruce Dern, Kurt Russell, Damian Lewis, Michael Madsen, Lena Dunham and Al Pacino.
Reviews, following its debut in Cannes in May, have been solid, with a Metacritic score of 85 out of 100, though according to CinemaScore, audiences have been slightly less celebratory, giving it a B score.
It’s currently standing at 85% Fresh on review aggregator site Rotten Tomatoes.
The movie, Tarantino's ninth, lands in the UK on August 14.