Scotland's Hamish Watson declared his intent to win something with Edinburgh after signing a new two-year deal which keeps him at the club until at least 2021.
The 27-year-old became the fifth player on Monday to commit his future to the capital outfit.
Bristol Bears back-row Nick Haining penned a two-year-deal and will the move north in the summer as will former South Africa under-20 hooker Mike Willemse.
The 26-year-old will join Edinburgh on a two-year deal from league rivals Southern Kings following the conclusion of the current Guinness PRO14 campaign.
Perpignan wing and Fiji Sevens star Eroni Sau joins the club on a two-year-deal as does Fiji Sevens captain Kalione Nasoko.
Williams, capped 25 times and who started at openside flanker in Scotland's Calcutta Cup encounter against England, said: "I couldn't see myself playing anywhere else in my career.
"I love it in Edinburgh. The playing group we've got, and are building, is absolutely amazing.
"We've got a great coaching staff and I want to win something with Edinburgh.
"If that takes two years or 10 years, it doesn't matter. This group of players and coaches is going places and I love the direction that the club is moving in."
Head coach Richard Cockerill added: "Hamish is one of the most exciting back-row players in the country, so it's fantastic that he'll be representing this club for years to come.
"He's a leader in the changing room and is so often a match-winner on the field.
"We're looking forward to watching him develop further and hopefully bring success to this city."
Haining is relishing the prospect of playing for Edinburgh next season.
He said: "When I spoke to Richard Cockerill about the direction of Edinburgh and the ambition of the club, it really excited me.
"I'm looking forward to moving to Edinburgh and starting pre-season in June - I can't wait to get stuck in."