The 20-year-old has signed a contract until June 2027 and Everton have paid a reported fee of £11 million for the defender, a record for Rangers.
Patterson has made six international appearances for Scotland but saw game time limited at club level this season as he was behind Rangers captain James Tavernier in the pecking order at Ibrox.
The Rangers academy product made his debut under Steven Gerrard and impressed with his performances in the Europa League while Tavernier was injured last season. Everton were interested in signing Patterson last summer but were unable to complete the deal.
“I’m over the moon to sign for Everton and looking forward to getting started,” Patterson told Everton’s official website.
“It was an easy choice to sign. This is a massive club with huge history and the fanbase is tremendous. Obviously we aren’t in the place where we want to be right now but we can definitely get there with the talent in the changing room and staff here, and I have full belief we can do that.”
Patterson becomes Everton’s second signing of the window following the arrival of Ukraine international left-back Vitalii Mykolenko from Dynamo Kyiv. The 20-year-old has been handed the number three jersey and will complete with club captain Seamus Coleman for a starting spot at Goodison Park.
Everton are 16th in the Premier League table following a difficult season under Rafael Benitez. The Toffees have won just one of their last 11 matches in the Premier League - a 2-1 win over Arsenal in December - and have slipped towards the relegation places.
“It is really exciting to come to a club that has huge talent in the team. I am going to work my socks off and hopefully I can do well with them in training and in games,” Patterson added.
“It was also great for me knowing the manager really wanted me here and that made my decision. When a club really wants you, it makes your mind up early on.
“I wanted to come here from the very start. I’m delighted to be here and really looking forward to playing in front of the fans at Goodison.
“Long-term, I want to nail down a starting position and win some trophies to make the fans proud.”
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