Williamson joined Scottish Rugby in early 2025 from private equity-owned education provider Inspiring Learning, where he was CEO.
Williamson previously ran the Goodwood Estate and is a former CEO of House of Fraser.
In May, Scottish Rugby confirmed Williamson was on “extended leave” from his job, without explaining why.
Scottish Rugby said on Thursday: “The board of Scottish Rugby has today dismissed Alex Williamson from his position as chief executive with immediate effect.
“His dismissal follows the conclusion of an independent investigation into matters that were brought to the board’s attention earlier this year.
“In light of the investigation findings the board of Scottish Rugby concluded that the CEO’s conduct had fallen significantly below the standards we set as an organisation.”
Last November, Scottish Rugby published its 2024-25 Annual Report showing its revenue rose £5.5 million to a record £79.4 million.
The organization’s loss after tax was reduced to £3.7 million, a year-on-year improvement of £7.6 million on the previous financial period.
Scottish Rugby’s cash of £28.2 million at June 2025 was an increase of £11.4 million on the prior year.