Connacht are replacing the departing Quinn Roux with Tongan international lock Leva Fifita.
Fifita, 31, has spent the past four seasons with Grenoble in France, having previously played for New Zealand side Waikato in the Mitre 10 Cup.
The second row, who started in Tonga's four games at the last World Cup, has 19 Test caps.
He says he is delighted to reunite with incoming Connacht forwards coach Dewald Senekal, who served as his head coach at Grenoble for two seasons.
“I’m very excited to be joining Connacht Rugby," said Fifita.
"I know Dewald very well from my time in Grenoble and after chatting to Andy Friend I believe this is the right step to make in my career.
"I’m looking forward to moving to the west of Ireland and play my part in helping the team succeed into the future.”
Head coach Friend explained his reasons for making the signing.
“In Leva Fifita we have been able to identify all the attributes we were looking for in a new lock," said the Aussie.
"He is a tall, strong athlete who will complement our existing second rowers, and also brings with him a good deal of experience at club and international level.
"We’re really pleased he has decided to join us and I know he will fit in nicely with the squad."
Roux, who first joined Connacht on loan at the start of the 2014/15 season, is Toulon-bound in the summer.
