The defender completed a move to Everton from Swansea City on Wednesday.
Swansea's Ashley Williams celebrates scoring their first goal
The Wales international made the move to Goodison Park on Wednesday, signing a three-year deal with the Toffees.
He comes in as a direct replacement for John Stones, who completed a big money move to Manchester City on Tuesday.
Ashley Williams celebrates scoring the second goal for Swansea City
He also adds some much needed experience to a relatively young Blues squad that lacked leadership under Roberto Martinez in the last two years.
And Koeman has hailed his latest signing, saying he is the kind of player that his side needs.
“He is an experienced defender and the kind of player we need in the team. He is a leader. He showed this at Swansea and he has shown it for his country.”
Everton's Phil Jagielka
It now remains to be seen if Williams’ leadership skills see him named as the new Everton captain.
Phil Jagielka currently occupies the role but Evertonians have consistently questioned whether he has the qualities to occupy the role, especially when they struggled under Roberto Martinez.
With Koeman speaking so highly of Williams’ leadership skills, perhaps he is considering a change in captain as a new era at Goodison Park gets properly underway.
Everton manager Ronaldo Koeman