In 2013, he was appointed chief executive of the Goodwood Group, the giant sporting estate in England and after for nine years moved to House of Fraser.
When Sport Direct’s Mike Ashley bought Frasers, he changed the management team and Williamson departed in late 2018, just over a year after he had started.
Since 2019, Williamson has been chief executive of Inspiring Learning – the UK’s largest provider of adventure camps for children.
“There are many opportunities ahead and I see no reason why Scotland cannot continue to be a positive force in the world game and within the wider sporting community,” he said. “I cannot wait to get to Edinburgh and crack on.”
Scottish Rugby said in July they expect to lose £10.6m this year and Williamson will follow David Nucifora’s autumn arrival in an advisory role on a two-year contract. Nucifora was previously Ireland’s performance director.
Scotland play Fiji, world champions South Africa, Portugal and Australia in November.
Their fifth straight home game will be against Italy in February’s Six Nations opener in February.