The film begins with the United Kingdom facing a brutal heatwave, while staying at the Dursleys', Harry Potter and Dudley are attacked by Dementors.

The Order of the Phoenix, a secret organisation founded by Albus Dumbledore, informs Harry that the Ministry of Magic is attempting to stonewall rumors about Lord Voldemort's return.

As Umbridge gains more control over the school, Ron and Hermione help Harry form "Dumbledore's Army", a secret group to teach students defensive spells.

When Harry hands it to Lucius, Sirius and Remus Lupin arrive with Order members, including Nymphadora Tonks, Kingsley Shacklebolt and Mad-Eye Moody.

Tom Felton, Jamie Waylett and Joshua Herdman play Slytherin students Draco Malfoy, Vincent Crabbe and Gregory Goyle.

[10][11] Yates believed he was approached because the studio saw him fit to handle an "edgy and emotional" film with a "political backstory", which some of his previous television projects including State of Play, Sex Traffic and The Girl in the Café demonstrated.

Evanna Lynch won the role of Luna Lovegood over 15,000 other girls who attended the open casting call,[24] waiting in a line of hopefuls that stretched a mile long.

[26] Persistent rumours linked Elizabeth Hurley to the role of Bellatrix Lestrange, although Warner Bros. asserted there was "no truth whatsoever" to reports that she had been cast.

[29] However, in April 2006 she revealed that she was three months pregnant and withdrew from the film because she would not have been able to perform the intense battle sequences in the Ministry of Magic in September and October 2006.

[32] MTV also reported about a month before the release of the final book that Kreacher, the Black family's house-elf, was cut from the film in one draft of the script.

At the US premiere of Goblet of Fire, series producer David Heyman said that former Hogwarts professor Gilderoy Lockhart, played by Kenneth Branagh in Harry Potter and the Chamber of Secrets, was in the first draft of the script for Phoenix.

Tiana Benjamin was scheduled to return for the film in the role of Angelina Johnson, the captain of the Gryffindor Quidditch team, but she had to withdraw due to a commitment to playing Chelsea Fox in EastEnders.

The atrium in the Ministry of Magic is over 200 feet in length, making it the largest and most expensive set built for the Potter film series to date.

[39][40] The set of Number Twelve, Grimmauld Place contains the Black family tapestry spread across three walls; when the producers told Rowling they wanted to visualise the details of each name and birth year, she faxed them a complete copy of the entire tree.

Working for six months on previsualisation starting in September 2005, Double Negative was largely responsible for sequences in the Room of Requirement, the Forbidden Forest, the Hall of Prophecies, and the Death Chamber.

[66] A new character in the film, Grawp, Hagrid's giant half-brother, came to life by a new technology called Soul Capturing, developed by Image Metrics.

[75] Cutting down the book to meet the time frame of the film, Goldenberg explained, became "clearer when [he] figured out that the organising principle of the screenplay was to narrate Harry's emotional journey".

[78] The scene at St Mungo's, the hospital where Harry and friends run into classmate Neville Longbottom and learn that his parents were tortured into insanity by Bellatrix Lestrange, was cut because it required the construction of a new set.

Also, to speed up the film's climax, several events in the Ministry leading up to Harry's battle with Voldemort were removed, including the brain room.

[74] Mrs. Weasley's encounter with a boggart at Grimmauld Place, Ron, Hermione and Malfoy becoming prefects, the appearance of Mundungus Fletcher, and Firenze teaching Divination followed suit.

In the novel, he is seen saving some of the Black family's artefacts which the Order of the Phoenix throw away, including a locket that ends up being extremely important in the seventh book.

[98] After the premiere, the three young stars of the film series, Radcliffe, Grint, and Watson, were honoured with a ceremony where their handprints, footprints, and "wandprints" were placed in the cement in front of Grauman's Chinese Theatre.

The package included a one-time-only code that activated a digital copy of the film, which may be played on a computer with Windows Media Player.

The site's critical consensus reads, "It's not easy to take the longest Harry Potter book and streamline it into the shortest HP movie, but director David Yates does a bang up job of it, creating an Order of the Phoenix that's entertaining and action-packed.

[145] Newcomer Evanna Lynch, playing Luna Lovegood, also received good word from a number of reviewers, including the New York Times, which declared her "spellbinding".

Rolling Stone's review also classified the film as better than the previous four instalments in the series, by losing the "candy-ass aspect" of the first two and "raising the bar" from the "heat and resonance" of the third and fourth.

[148] Peter Travers of Rolling Stone called the film "the best of the series so far, [with] the laughs, the jitters and the juice to make even nonbelievers wild about Harry".

[148] Leo Lewis of The Times (London) expressed disappointment that the three main actors were not able to fully advance the emotional sides of their respective characters, weakening the film.

[146] The San Francisco Chronicle complained about a "lousy" storyline, alleging that the first twenty minutes of the film, when Harry is put on trial for performing magic outside of school and threatened with expulsion, but is cleared of all charges, did not advance the plot.

The review also criticised the under use of the "cream of British acting", noting the brief appearances of Helena Bonham Carter, Maggie Smith, Emma Thompson, David Thewlis, Richard Griffiths, and Julie Walters.