The Swedish ro-ro group said Tomas Bergendahl had "terminated his employment", without giving a reason..
He will remain in his position until 31 May.
Bergendahl has been with RABT since 2013 and owns 75,000 of its B shares.
The owner has already started the recruitment process to find a replacement.
RABT earned SEK 170m ($23m) in the third quarter, up from SEK 43m a year ago.
