A long school break has been kind to Harry Potter.

After a two-year gap since the last film, Harry Potter and the Half-Blood Prince opened with a whopping US$58.4 million domestically in its first day. That's the best single-day haul yet for the franchise and the fourth-best daily gross ever.

Receipts include a record US$22.2 million from midnight screenings alone.

The sixth instalment in the Harry Potter series had the second-highest debut ever for a movie opening on Wednesday. It trailed only Transformers: Revenge of the Fallen, which premiered with US$62 million last month.

The two-year lag since the fifth Harry Potter movie was the longest in the franchise's history.