The 20-year-old, who first joined Everton at the age of five, has signed a three-year deal at Turf Moor for an undisclosed fee.
Long celebrates a goal for Brentford with former England U20s team-mate Alex Pritchard in 2015
And he will link up with the Clarets squad as they prepare for their Championship campaign, which begins with a game at Leeds United on Saturday 8 August.
Long is no stranger to the second tier, having played the majority of his senior football in that division during a loan spell with Brentford last season.
Prior to that, the Huyton-born striker had spent time on loan with MK Dons in League One after bursting through Everton’s academy as a regular goalscorer for their junior teams.
"I’m absolutely buzzing to have officially signed and I can’t wait to get started," Long told BurnleyFC.com
"I can’t thank Everton enough for what they did for me, but I think it’s time to start a new chapter in my life and I can’t wait to get started with Burnley.
"I’ve proved that I can score goals in the Championship and I only had two starts. I would have started more without injuries and I’m looking forward to scoring goals for Burnley.
The new Burnley striker's last goal for England came last October in the U20s' 3-2 win over the Netherlands.
"I’m fresh, young and eager to succeed to be honest and I just want to show the Burnley fans what I can do."
Long has also been a regular for England over the years, after first representing the Three Lions at U16 level in the Victory Shield in 2010.
He’s since won caps at U17, U18, U19 and U20 level, featuring in the U20 World Cup of 2013 and under Aidy Boothroyd last term when he scored against the Netherlands in October 2014.
Long is now eligible for Gareth Southgate’s U21 squad, who start their new campaign with a game against the USA U23s at Preston North End’s Deepdale on Thursday 3 September.
Tickets for that game are on sale now, so click here for more details.
