The 34-year-old, who has played 103 Tests for Australia, enjoyed a hugely successful and lucrative stay in France, playing a major role as the wealthy southern club won the European Rugby Champions Cup three times.
Suntory were once coached by England coach Eddie Jones, who handed Giteau his Test debut in 2002 and previously employed George Gregan, while Wallabies flanker George Smith is still on the books at the club.
