Professor Richard B Davies, who has held the role at the university since 2003, stood aside for an internal investigation to be carried out.
The dean of the school of management, Marc Clement, and two other members of staff, have also been suspended.
All four have been suspended on full pay.
In an email, seen by BBC Wales, staff were told by registrar Andrew Rhodes, that the matters being looked into did not concern “the academic performance of the university or its financial wellbeing”.
Mr Rhodes is to take on vice-chancellor duties on an interim basis.
He added: “I appreciate that a lot of questions will arise from this message, but it will not be possible to provide more detail at this time.
Prof Davies, who was brought up in West Wales, studied Engineering at Cambridge before getting a PhD at Bristol University.
Llanelli-born Mr Clement has held several senior academic positions and was appointed dean of the school of management in 2015.