The Costa Rica international goalkeeper joins the Ligue 1 champions for a reported €15 million (£13.6m/$16.5m) fee, with Alphonse Arreola also heading to Madrid on a loan deal.
Navas became a fans' favorite at Real Madrid after joining from Levante in 2014 following a string of impressive performances at the 2014 World Cup.
The 32-year-old shot-stopper enjoyed enormous success with the Bernabeu outfit, winning three consecutive Champions League titles, along with one LaLiga title and two UEFA Super Cups.
However, the arrival of Thibaut Courtois at the beginning of the 2017/18 season limited Navas' first-team opportunities.
More to follow...