Jones turns 34 in September on the eve of the Rugby World Cup. "It is the right decision for my career at this point in time, along with my personal ambitions on and off the field, my welfare and needs of my family," Jones said on Tuesday.
He was voted the best player of the Six Nations. He played through knee ligament damage to help Wales beat Ireland 25-7 and clinch the grand slam. Jones has 125 caps for Wales since his 2006 debut. He needs five more to become the most capped Wales international.
The lock could become the most capped rugby international next year, surpassing Richie McCaw's record tally of 148. Playing to 2021 will also put Jones in the running for a fourth British and Irish Lions tour. The Lions tour South Africa that year. Gatland, who has already agreed to coach them again, has said Jones is a contender to be the Lions captain.
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