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Catt, 27, came through the club's academy and Auterac, 23, joined from Saracens ahead of the 2014-15 season.
"It's fantastic to be retaining Nathan and Nick, two outstanding young props," said Bath head coach Mike Ford.
"They both have their best years ahead of them and with Neal Hatley overseeing their development, they'll keep going from strength to strength."
Bath loosehead props Nick Auterac and Nathan Catt have signed new contracts with the Premiership club.