The La Liga champions triggered Lenglet's €35.9m release clause before agreeing terms with the centre-back on a five-year contract, which includes a new release clause of €300m.
The French worldwide joined Sevilla from Nancy in January 2017 and scored four goals in 52 games last season.More news: Netflix Topples HBO in Emmy Nominations
The French global is set to sign a five-year contract with the Catalans.
Manchester United were also credited with an interest in securing his signature, but Lenglet has opted to stay in La Liga with Barca.
La Blaugrana paid Lenglet's full €35m release clause after failing to negotiate a lower fee for the France global.More news: Now-Hurricane Chris Poses Possible Threat to Nova Scotia and Newfoundland-Labrador
The 23-year-old joins a growing French contingent at Camp Nou, including forward Ousmane Dembele, and defenders Lucas Digne and Samuel Umtiti.
He is yet to be capped by France at senior level but has won 10 caps at Under-21 level.
Spanish giants FC Barcelona have already signed one player ahead of the 2018/19 season, but has a second acquisition of theirs now been revealed?More news: Trumps kick off United Kingdom visit with black-tie gala
He becomes the second new arrival of the week after Arthur.
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