Weighing 122kgs, Gough will bring plenty of size and physicality to the Irish pack along with his wealth of experience.
During an illustrious career, that has included 64 caps for Wales, the second row forward has played for Pontypridd, Newport and spent the last six seasons with the Ospreys.
Gough flourished for Wales during their 2008 Grand Sam triumph where his dominant presence in the set piece was a pivotal role in their success.
London Irish Director of Rugby Brian Smith said: “It’s great to have a player of the stature and experience of Ian onboard. He is a proven Test forward and has been exceptional at the set piece and the breakdown area throughout his career. His presence and influence around the training ground will be massive. He’ll add more experience to our young, talented squad.”