Riddell started his career with St George-Illawarra before joining Eels for four years ago, where he since made 77 games appearances.
Wigan chairman Ian Lenagan, who concluded the deal in Sydney last night, said: "Mark is exactly the hooker we need to lead our forwards and to further develop young Michael McIlorum.

"He adds strength and size, brings spark to our attack and is a hard-working defender who plays considerable game time.
"His kicking from hand and goal kicking skills are an additional benefit.

"Mark is a great character on the field who will go down very well with the Wigan fans and is looking forward to testing himself in Super League."
Riddell said: "Wigan is the biggest name in world rugby and it is a wonderful opportunity for me.

"I am sad to be leaving Eels after four massively enjoyable years and aim to finish my time with them this season on a high."
Wigan also continue to being linked with a move for Queensland State of Origin forward Carl Webb.

Webb, currently playing for North Queensland Cowboys said: "I take every offer seriously. I would have to look at what's on the table first, but I said right at the start of negotiations that I would consider deals from overseas."

Webb, 27, and weighing in at 108kg – the same as Iafeta Palea'aesina – is a hefty unit, yet mobile too.

Meanwhile, Wigan have dismissed speculation that Trent Barrett has already agreed to join Cronulla Sharks for the 2009 season.
Lenagan met Barrett's agent Wayne Beavis earlier this week to discuss the player's future after Wigan confirmed the stand-off would be allowed to leave the JJB in September.

New sensation Sam Tomkins has been quick to pay tribute to Barrett after exploding on to the scene in dramatic style with a five-try debut against Whitehaven on Monday.

Despite a hat-trick from Barrett, the star of the show was undoubtedly
19-year-old, Tomkins.
But the teenager has hailed the contribution of Barrett, as well as that of his elder brother Joel, a young back-rower who did not play against Haven but whose advice he sought in the lead-up to the game.

The former Wigan St Patrick's youngster said: "Trent is one of the world's best players at the moment.
"Just to play with him is an honour. You pick up so much off him and he's just a great player to play with.
"Joel was so supportive when I found out I was playing and really tipped me up on what to do – don't try and do too much, nothing silly. He's been a big help."