The 24-year-old England international becomes the first man to go down what could become a well-trodden path with the Super League club and Premiership champions announcing details of a link-up which incorporates co-operation between the respective coaching teams and academies, player loans and a cross-code match.
Tomkins' move represents quite a coup for Sarries, who benefited from the player's desire to try his luck in rugby union.
He said: "I will always be a proud Wiganer, but everybody in rugby union and rugby league can see there is something very special happening at Saracens, and I can't wait to be part of it."
Wigan chairman Ian Lenagan added: "Joel wished to move to the south of England and take his chance at rugby union.
"Wigan would not step in the way of a player with such clear ideas to leave. He is joining an excellent club in Saracens.
"Wigan has grown close with Saracens through these and previous discussions and we are delighted and excited by the partnership between Wigan and Saracens we are announcing today.
"Both games have their own place separately but the synergy available from these two leading clubs working together is exceptional."
Saracens chairman Nigel Wray said: "Wigan are a fantastic rugby club with a fantastic worldwide reputation, and we are really excited by the potential of this partnership as we share resources and knowledge to ensure each club is able to maximise its potential on and off the field."
Gilbert has released a new line of rugby cleats. The Gilbert Virtuo 8S is part of the exciting new product. Check it out.
The Barbarians are one of the top invitational rugby sides with a long history and classic rugby jersey.
The Nike Tiempo is a solid rugby cleat and one of few styles still made from full-grain natural leather.
The Lions get ready for their matches with this green training jersey. It's what the players wear. Get in the Gear!
A cool looking all black rugby cleat with the high performance adidas is known for. Get in the Gear!
Wear the crest of the British and Irish Lions on your t-shirt. A great look for the summer.
$29.99
The Lions are ready to get their Australia tour underway. They arrive in Perth on Monday.
The New Zealand All Blacks training jersey for 2013/14. Get in the Gear!
The USA Rugby Pro Alternate rugby jersey is perfect for any fan of the Eagles. Get yours to wear during the summer Test matches.
The NEW All Blacks 2013/14 jersey has arrived at World Rugby Shop. Dare to wear the colors of the All Blacks.
