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The pair scored 456.81 to finish ahead of Russia (445.23) and Ukraine (439.86).
Earlier, Tonia Couch and Georgia Ward secured silver and bronze medals respectively in the individual 10m platform final.
It takes Britain's total to seven medals with two days still remaining.
Laugher and Mears won World Championship bronze together last summer but had their pre-season disrupted after Laugher suffered a foot injury in training.
They showed impressive form at the final World Series in Kazan in April - where they won silver - but Laugher had been disappointed with his individual silver on Thursday after struggling with cramp.
"That's a personal best score for us and it means everything to get this result with my best mate," Laugher told BBC Sport.
"If anything the silver just added to the fire and I wanted it even more tonight."
Mears added: "We haven't had a huge amount of preparation coming into this event, but a score like that really sends out a message to the rest of the world."
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Despite a near 10-year professional career, Couch's silver was her first individual 10m European honour.
"This means so much to me," she said. "I had a terrible start and needed a real talk with myself, but I managed to pull it back and I'm so proud of that result."
Ward, who is competing as a senior British diver for the first time this season, secured Team GB a berth in the event for Rio 2016 earlier this year.
"I'm in shock really," she said. "I am loving every moment and diving in front of my home crowd was amazing but I need to keep this going to secure an Olympic place."
On Saturday, Ward will return alongside Matty Lee in the mixed synchronised 10m platform final - having won 3m bronze together on Monday.
Sunday's final day will see 10m Olympic bronze medallist Tom Daley as well as Commonwealth 3m champions Rebecca Gallantree and Alicia Blagg battle for honours.
British divers Jack Laugher and Chris Mears won 3m synchronised springboard gold to continue the hosts' incredible European Championships in London.