Gibson was heavily linked with a move way from Middlesbrough in the close-season following their relegation from the Premier League.
West Brom had multiple bids for the centre-back rejected while a number of top-flight clubs were credited with an interest in the 24-year-old, who earned his first call-up to the England squad in March and was again selected in June.
Gibson, who is still waiting for his first senior cap, was already tied to Boro until 2021 but, after signing fresh terms with the club, he told their official website: “I’m delighted to sign a new contract.
“Everyone knows what this club means to me. I’ve grown up with the club, I went to the Riverside from a young age and remember all those special European nights.
“I’ve been lucky enough to go on and play for the club, and even the captain team, and I’ve had some amazing experiences here.”