Czech Republic midfielder Tomas Soucek from Slavia Prague has been signed on loan with an option to buy.
The 24-year-old has scored 10 goals in 19 appearances for Slavia this season and could cost us £13m.
Manager David Moyes said Soucek, who has 25 international caps, “fits the profile of the player we want”.
West Ham are 17th in the Premier League table, outside of the relegation places only on goal difference.
“We are in a difficult period where we need experienced players. At the moment he [Soucek] ticks a lot of boxes. We need to give him an opportunity and time to settle in.”David Moyes