The club announced the news via Twitter on Saturday:
West Ham United @WestHamUtd
#WelcomeMarko https://t.co/hbytCapBe22017-7-22 16:54:13
Per Stoke City's official website, Arnautovic will cost the Hammers at least £20 million, with £5 million in bonus money added to the deal. The fee is a club record.
The Austrian will be a huge miss for Stoke. He scored six goals and provided five assists in 32 Premier League appearances last season, per WhoScored.com.
However, he will bring creativity to a West Ham attack that managed only 47 goals in 38 Premier League games last season, as illustrated by Opta:
190 – Marko Arnautovic has led the way for Stoke for chances created in each of his four seasons in the PL (190 in total). Vital. https://t.co/EaBlZwb9OF2017-7-12 08:55:23
West Ham appear keen to strengthen their forward line this summer, having also been linked with a move for Arsenal striker Olivier Giroud and Bayer Leverkusen's Javier Hernandez, per Matt Law at the Telegraph.