Businessmen David Gold and David Sullivan, former owners of Birmingham City, completed their takeover of the Premier League strugglers and said they wanted to take the club into the Champions League within seven years.
They also plan to move West Ham from Upton Park to the new Olympic Stadium just three miles away after the 2012 London Games.
"We care passionately about this club, we are so pleased to be here," he said, adding there were no plans to replace manager Gianfranco Zola.
"He is the manager and will stay as the manager," he said. "But we must stay in the Premiership, if we don't it is an absolute disaster for us."
West Ham may be one of London's biggest clubs but have mainly lived in the shadow of Arsenal, Tottenham Hotspur and Chelsea and have never won the title in their 110-year existence, unlike the other three.
Hammers fans loyally maintain they "won" the World Cup in 1966 with their trio of Bobby Moore, Geoff Hurst and Martin Peters in the triumphant England team, and they have also enjoyed cup successes.
Three-times FA Cup winners, they lifted the European Cup Winners' Cup in 1965 but since 1978 they have been relegated from the top flight four times and have never finished higher than ninth since regaining their Premier League place in 2005.
Sullivan wants to maintain West Ham's traditions and take them to the heights of the English game.
"West Ham is the club of the East End and Essex. I went to school in Hornchurch and right out into Essex is West Ham land," said Sullivan.
"It is 30 miles but we hope all those people who live there and feel passionate, get behind the club. We will not make the mistakes others have made in the past."
