A 6'8" forward, the 28-year-old also featured for Northampton Saints before switching to the Ricoh Arena, playing 93 games across six seasons before his move to the Guinness PRO12.
"James has been part of a competitive mix of second row players at Wasps but has shown his talent when given the chance," said Lam.
"He brings a vast amount of experience from playing in both the Aviva Premiership and European Champions Cup and will greatly boost our second-row options. We're all looking forward to welcoming him to Connacht Rugby."
Connacht have had a frustrating start to the defence of their Guinness PRO12 crown, losing their first four games to sit bottom of the table.
But with a debut season in the European Champions Cup to look forward to, Cannon feels it's a good time to be joining the region.
He said: "I'm very excited about the new challenge in Connacht and look forward to working hard to try to get more first team opportunities and to play my part within the squad."
Guinness PRO12 Connacht News
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