The Demark international has signed a three-year deal with the Toffees that will take him through to the summer of 2022.
He will join up with his new club on July 1 and begin preparations for next season, where he is expected to provide cover and competition for first-choice shot-stopper Jordan Pickford.
Lossl made 31 Premier League appearances for Huddersfield in 2018-19 but was unable to prevent their relegation to the Championship, conceding 54 goals and keeping just five clean sheets in that period.
He joined on loan from German outfit Mainz in the summer of 2017 following the Terriers' promotion to the top flight, a deal which was made permanent a year later.
Pickford’s current competition comes in the form of 36-year-old Maarten Stekelenburg, who made just two appearances all season, both in the Carabao Cup.
England international Pickford has won the hearts of Everton fans but has made some high-profile blunders, particularly his error to allow Liverpool striker Divock Origi to head in the winner in the Merseyside derby at Anfield in December.
Lossl represents the Toffees’ first signing of the summer, although they have been tipped to move for a right-back, with current incumbent Seamus Coleman now 30 and without a quality alternative.
For Huddersfield, Lossl is one of six senior players to leave the club upon the expiry of their contracts, with left-backs Chris Lowe - who has already agreed a move to Dynamo Dresden - and Erik Durm, striker Laurent Depoitre and midfielders Jack Payne and Danny Williams also departing.
Isaac Mbenza and Jason Puncheon also leave the Terriers as their respective loan spells come to an end.