The 6’3’’ central defender joins the club on a three-year deal after completeing a medical and agreeing personal terms on Thursday.
Reid hit the headlines with a late equaliser in New Zealand’s impressive World Cup campaign.
Speaking to the official site following his unveiling to the media he said, “I am looking forward to getting started.
“My dream has been to come and play in the Premier League and I am happy that I am a West Ham player.
“It has been a mad couple of weeks and the last couple of days have been pretty hectic, so I am just happy to be here now. I am pretty decent fitness-wise. I had a game last Sunday so I am in pretty good nick.
“The World Cup was a life-changing experience and something I will remember forever. I want to bring the positives from that here on the pitch at West Ham.
“This club has great history and the league is one of the best in the world. I am looking forward to the challenge ahead.”