Ocon will partner Sergio Perez following Nico Hulkenberg's move to join Renault next season.
Ocon, 20, will partner Mexican Sergio Perez following German Nico Hulkenberg's move to join Renault next season.
The Silverstone-based team said Ocon had agreed a multi-year deal.
"I'm very excited to be joining Force India," said Ocon, who started 2016 as a test driver with Renault and as a race driver for Mercedes in the German DTM Touring Car series.
"I know the team quite well already because I was a test driver last year and I'm really looking forward to working with everybody at Silverstone once again.
"I'm still relatively new to Formula One, but spending half a season at Manor Racing has given me some valuable experience and I feel ready for this new opportunity with Force India."
Ocon is a former European Formula Three and GP3 champion.
"It's something I've been working towards my whole life and I intend to grab this opportunity with both hands, so that I can deliver the results the team expects from me.
"I want to say 'thank you' to everybody at Manor and especially to Mercedes-Benz for their support and belief in me. I can't wait for 2017 and my first full season racing in F1."
Paddock speculation had suggested that Ocon would go to Renault, but Hulkenberg's move ended that and Renault has since confirmed it will retain Briton Jolyon Palmer alongside the German.
In other moves, Sauber appears likely to retain its current driver line-up of Swede Marcus Ericsson and Brazilian Felipe Nasr while the American Haas team is poised to confirm the signing of Dane Kevin Magnussen, who is leaving Renault.