The 31-year-old lock has made 62 international Test appearances, playing at both the 2011 and 2015 World Cups.
Nemsadze has also played for Montauban and Valence d'Agen among others.
Bristol director of rugby Andy Robinson said Nemsadze, at 6ft 5ins and weighing more than 120kg, "fits the bill for a Premiership lock".
Robinson continued: "He's heavy, abrasive and he's been a key part of a Georgia forward pack that has enjoyed considerable success at international level.
"We recruit players that fit the mould of the standards and culture we expect at Bristol Rugby. Giorgi not only brings with him the knowledge of playing in France for nearly 10 years, but also that physical intensity we are striving for."
Premiership newcomers Bristol have signed Georgia international lock Giorgi Nemsadze from French second-tier side Tarbes.