Sheridan was released by Leeds Rhinos after being told he had no future at Headingley.

The 27-year-old scrum-half has signed a two-year contract with the Vikings, who will officially unveil their biggest close-season recruit at press conference on Monday.

"It's a very, very significant signing," said Widnes coach Neil Kelly.

"It's very rare that players of his calibre and quality become available and it's great to be able to attract him.

"It shows the increasing stature of Widnes," he added.

"Ryan played for Great Britain this year and he still has ambitions on the representative front. We like to think we can help him in those ambitions."

Sheridan scored 59 tries in 154 appearances for the Rhinos after signing from Sheffield Eagles in 1996 and was a member of Leeds' 1999 Challenge Cup-winning team.

He played for Ireland in the 2000 World Cup and captained Yorkshire in this year's Origin Series.

Sheridan has been released from his contract at Leeds to make way for Rob Burrow, Danny McGuire and new signing Andrew Dunemann.

He is one of four victims of a close-season clear-out by coach Daryl Powell, who is also looking to offload Great Britain winger Karl Pratt, second-rower Andy Hay and prop forward Darren Fleary.

Like Sheridan, Hay has been released from the final year of his contract at Headingley and is another possible target for Widnes.

"We have an interest in him," said Kelly, who may have to fight Castleford for the former Great Britain international's services.

"I'll be speaking to my chairman over the weekend and hopefully we can work something out," he said.