LOS ANGELES, July 12 (Reuters) - "Harry Potter and the Order of the Phoenix" worked like magic in its U.S. box office debut, whipping up $44.8 million for the biggest Wednesday ever, according to studio estimates released on Thursday.

"Order of the Phoenix," based on the best-selling novel by British author J.K. Rowling, also proved an international sensation with an estimated $29.2 million in ticket sales for a worldwide, one-day haul of $74 million.

The numbers include midnight screenings in the United States and Canada that brought in $12 million.

The previous record for a Wednesday in the United States was 2004's "Spider-Man 2" with $40.4 million, according to box office tracker Media By Numbers.

The latest Potter movie, the fifth in the wildly popular series, has British boy wizard Harry flummoxed by his mates at the Hogwarts School of Wizardry and Witchcraft who doubt his near-death battle with the evil Lord Voldemort.

"Harry Potter and the Order of the Phoenix" was produced and distributed by Warner Bros., a unit of Time Warner Inc..

The first four Potter movies, starting with 2001's "Harry Potter and the Sorcerer's Stone," have collectively generated $3.5 billion in worldwide ticket sales for Warner Bros.

REUTERS