The Ivory Coast international, 23, is being lined up as a replacement for the departed Idrissa Gueye, with reports suggesting he could cost up to £27.5m.

Gbamin moved to Mainz in 2016 from Lens and made 86 Bundesliga appearances for the club, scoring three goals.

It is understood he has had a medical and is set to sign a five-year deal, with Everton hopeful of completing his switch in the next 24 hours.

A deal to sign Juventus striker Moise Kean is also likely in the next few days.

Gbamin was part of the Ivory Coast squad at the recent Africa Cup of Nations in Egypt and made three appearances for the Elephants as they reached the quarter-finals.

Toffees manager Marco Silva has already signed midfielders Fabian Delph, for a fee worth up to £10m, and Andre Gomes from Barcelona in a £22m deal.