Jonjoe Kenny will also go after rejecting a new deal but Asmir Begovic is staying at Goodison Park after the club triggered an option to extend his contract for a year.
Midfielder Delph, who cost £8 million from Manchester City, made just 41 appearances in an injury-hit three-year spell on Merseyside but while he played a key role in the wins over Manchester United, Chelsea and Leicester that helped keep Everton up, he was not offered an extended deal.
Sigurdsson was a club record signing, costing £45 million in the summer of 2017 when Everton brought in three No. 10s, along with Wayne Rooney and Davy Klaassen.
The Iceland international scored 31 goals in 156 games for the club, with a best of 14 in 2018-19, but did not play last season.
Forward Tosun was bought by Sam Allardyce in January 2018 for £27 million but made just 61 appearances for Everton and only scored 11 goals, while suffering from injuries and being loaned to Crystal Palace and Besiktas.
Owner Farhad Moshiri published an apology to the club’s fans this week in a message when he referred to mistakes they made in the transfer market. “We have not always spent significant amounts of money wisely,” he wrote.
Everton are aiming to get more value for money in recruitment and to build a younger squad. Delph, Sigurdsson and Tosun are all over 30.
Full-back Kenny, who is 25, featured 21 times last season, including 14 appearances under Frank Lampard, and Everton offered him an extended deal.
But Liverpudlian, a product of the club’s youth system, opted to move on in pursuit of first-team football. Kenny, who has had previous loan spells at Schalke and Celtic, risked becoming third-choice right-back behind captain Seamus Coleman and January signing Nathan Patterson.
Goalkeeper Begovic will remain as understudy to Jordan Pickford, while the third choice, Andy Lonergan, has been offered a new deal to stay. Everton are also in talks with Lewis Gibson about a new deal.
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