More than 300 Santander branches will move from being open from 9.30am to 4pm on Saturdays to operating a half day service, closing at 12.30pm.
Branches will also operate from 9.30am to 3pm on weekdays, instead of until 4.30pm.
The move is part of a wider shake-up of changes to opening hours being introduced by the bank from July 18.
The bank said branch staff will still be available for pre-booked face-to-face appointments between 3pm and 5pm.
Santander added there will be no compulsory redundancies or a reduction of employee working hours as a result.
Here is a list of locations provided by Santander where branch opening hours will be moving to half day opening in Lancashire: