On-loan Southampton winger Theo Walcott will sign a permanent two-year deal at the club when his Everton contract expires at the end of the season.
Walcott, 32, returned to St Mary's on a season-long loan in October, 15 years after making his debut for the Saints as a 16-year-old.
He has scored three goals in 22 games for the club so far this season.
"I'm not sure I can properly express how happy I am about this," said Walcott, who has 47 England caps.
"Southampton is a club that means so much to me, and it has been incredibly special for me to have spent this season back at St Mary's. But to now have the opportunity to return for a further two years means such a great deal to me, both personally and professionally.
"I would like to say a huge thank you to the club, my teammates and the fans for making me feel so welcome back here, and I can't wait to continue pulling on the shirt in the next couple of seasons. Hopefully in that time we can make a few more special memories too.
"I would also like to say thank you to everyone at Everton, who have been so good to me throughout my time with the club, and I wish them every success in the future."
Having come through the club's academy, Walcott became the Saints' youngest-ever first-team player when he made his senior debut aged 16 years and 143 days in August 2005.
The winger left for Arsenal in 2006, going on to score 108 goals in 397 appearances over 12 years, before moving to Everton in a £20m deal in January 2018.
He returned to the south coast on transfer deadline day last autumn after struggling for regular first-team football at Goodison Park.
"Theo has been a very good influence for us this season. He is a very professional player who does things in the right way and has a very positive impact not only on our young players but on the dressing room as a whole," said Southampton boss Ralph Hasenhuttl.
"He understands the way we want to play, he has shown great commitment and he has also shown how he can be an important part of our game. I think he is a player who can continue to help us in these next two years, so I am pleased that he has agreed to stay with us."
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