The news of left-back Baines' new deal is a timely boost for Everton fans as it comes on the eve of Tuesday's Merseyside derby against Liverpool at Anfield in the Premier League.
Manager Roberto Martinez said: "From every angle you look at it, to have Leighton here for the long-term is an incredible boost.
"We're delighted Leighton has signed for the next four years. It gives us a great boost internally and also for the fans.
"He is so important with his daily standards and with the younger players. His best is still to come."
The 29-year-old, who had 17 months remaining on his previous deal, moved to Everton from Wigan Athletic in 2007 and has made 263 appearances in all competitions for the club, scoring 25 goals.
Baines has repeatedly been linked with a move to Manchester United, particularly after former Everton manager David Moyes headed to Old Trafford, but has now put speculation over his future to bed.
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