The Ivory Coast international returns to the Eredivisie for a fee of €22.5million (£20.2m) just 18 months after becoming the most expensive signing in Hammers history when he joined in a £45m transfer from Bundesliga outfit Eintracht Frankfurt.
Haller largely struggled to adapt to the Premier League and leaves West Ham with a record of 14 goals in 53 appearances across all competitions, having recently failed to impress as a stand-in for injured talisman Michail Antonio.
Sébastien Haller has joined Ajax on a permanent basis for an undisclosed fee.
We would like to thank @HallerSeb for his contribution to the Club and wish him all the best for his future career.
— West Ham United (@WestHam) January 8, 2021
In a statement, the Hammers said: “West Ham United would like to thank Sébastien for his contribution to the Club and wish him all the best for his future career.”
Haller has signed a contract at Ajax lasting until the summer of 2025 and is excited to return to the Eredivisie, where he previously starred during a goal-laden two-and-a-half year spell at Utrecht.
“Happy to announce my arrival at this iconic club @afcajax and i can’t wait to start playing in this mythical stadium,” Haller wrote on Twitter.
Haller joins an Ajax side that currently sit first in the Dutch top-flight under manager Erik ten Hag, one point clear of rivals PSV Eindhoven as they seek a 35th domestic title.
— Sébastien Haller (@HallerSeb) January 8, 2021
The Amsterdam outfit are also through to the last 32 of the Europa League and face French side Lille in February.
Standard Sport understands that West Ham were willing to take a sizable financial hit on their record signing, with manager David Moyes set to be permitted to quickly reinvest the funds in a replacement more similar in style to Antonio.
The Hammers - also set to sell Robert Snodgrass to Sam Allardyce’s West Brom - have been linked with Bournemouth striker Josh King as well as the likes of Marko Arnautovic, Graziano Pelle and, most recently, Lyon’s Moussa Dembele.