The Costa Rica international signed an initial four-year deal in 2019 when he joined PSG from Real Madrid.
The 34-year-old has continued to excel in Europe's premier club competition since joining PSG, though.
Navas played nine of his side's 12 games as they reached the final last season, losing to Bayern Munich, and has been outstanding in their run to the 2020-21 semi-finals.
No goalkeeper in the Champions League this season has faced more shots (157) or made more saves (47) than Navas.
He has prevented 4.9 non-penalty goals, using expected goals on target (xGOT) data, including 2.2 in the quarter-final first-leg win against Bayern alone.
Only opposite number Manuel Neuer (5.2) has prevented more goals than Navas, who also saved a penalty from Lionel Messi in the last 16.
News of his new deal comes as the PSG goalkeeper prepares to face Manchester City in the last four, having returned from injury against Metz on Saturday.