SANTA MARIA, Calif. – Actor Macaulay Culkin – the first real “star” witness in Michael Jackson’s child-molestation trial – is set to take the stand today to boost the pop icon’s defense.

The 24-year-old “Home Alone” star is expected to say he was never molested or improperly touched by Jackson, 46, during his many boyhood sleepovers at the singer’s Neverland Ranch.

“Mac has always said ‘nothing happened.’ He has never wavered on that. He’s not happy about coming to court, but he wants to set the record straight, as much for himself as for Michael,” a source told the Daily News.

Culkin, who was busted for pot and pill possession last fall, was reportedly “disgusted” by recent testimony from two ex-Neverland employees, former cook Phillipe Lamarque and ex-maid Adrian McManus, who said they saw Jackson fondle and kiss him in the early 1990s.

Culkin, who is godfather to Jackson’s oldest son, 8-year-old Prince Michael I, has said his visits to Neverland were filled with “innocent fun” like water balloon and food fights – not fondling. In a May 2004 appearance on “Larry King Live,” Culkin said his friend Jackson is misunderstood by most people.

“Macaulay gets Michael like few people do. They both come from big families. He knows the pressures Michael grew up with, working from a young age, becoming a star and making lots of money,” said a source familiar with the pop star.

Jackson is accused of giving booze to and molesting a 13-year-old cancer survivor while conspiring to hold the boy and his family hostage at Neverland in early 2003. He denies all charges.

Culkin’s long-awaited testimony will follow two dull days of testimony from Neverland staffers, who said the accuser and his family were never held against their will.