In the rousing new production of “The Pirates of Penzance” at 5th Avenue Theatre, actor Brandon O’Neill is every inch a pirate king. And yes, as the song goes, it is “a glorious thing to be a pirate king” — for him and the audience watching him.

O’Neill, a Seattle native who has matured into a first-rate musical-theater leading man, was a no-brainer for this role. From his strapping physique to his soaring voice and flair for clowning, he fills those pirate boots with panache.

When required to swashbuckle, he brandishes a fencing foil with the best. And when this leader of a not-so-bloodthirsty brigand band joshes, cowers and double-takes, O’Neill is a stitch.

And he’s in excellent company.

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Well cast, and featuring a full orchestra and a large company, this “Pirates of Penzance” is colorful to the eye, generally sweet to the ear and very amusing. It introduces you to (or reminds you of) why this is one of the most popular and revived operettas by the golden team of writer W.S. Gilbert and composer Arthur Sullivan, in its colorful story and impish satire of British manners.

Director-choreographer James Rocco goes for the gusto in every moment of the enchantingly ridiculous story of Frederic (terrific Broadway comer Hunter Ryan Herdlicka), who after 21 years as an apprentice pirate believes he has fulfilled his contract and can now “go straight.” (Too bad he has to throw overboard his loyal nursemaid, played endearingly by Anne Allgood, to get on with it.)

The attractions of life on terra firma increase when a gaggle of pretty, giddy young English sisters appear in the cove where Frederic’s cohorts have dropped him off. That brood includes such winning performers as the ebullient 5th Ave veteran Billie Wildrick (who now commutes between New York and Seattle), and the fine soprano Anne Eisendrath as spunky ingénue Mabel, who makes beautiful music with Frederic.

Gilbert’s brilliant lyrics are not all articulated crisply, and the sound system promotes a bit of shrillness in Eisendrath’s truly stratospheric high-high register. But she and the other singers do right by the lovely, witty arias (i.e., “Poor Wandering One”) and duets.

The orchestra is in excellent form, and the choral numbers are fully voiced delights, including the bracing pirate odes (“With Cat-Like Tread,” with a melody purloined later for “Hail, Hail, the Gang’s All Here”) and a regimental march by bumbling bobbies, here transformed into bumbling Mounties led with Dudley Do-Right rectitude by Jared Michael Brown.

“Pirates of Penzance” also boasts the best patter song in the G&S repertoire (which is saying a lot), “I Am the Very Model of a Modern Major General.” As the decorated patriarch of Mabel and company, David Pichette must deliver this formidable tongue-twister, then reprise part of it in double-time. He beats the clock, with an impish little twirl of a red parasol, but the rush of lyrics are hard to make out.

The show is a visual treat, thanks to Rocco’s romping line dances and freeze-frame tableaus, Tom Sturge’s

lighting and charming Victorian-style sets, and Christine Tschirgi’s

eye-catching costumes. The 5th Avenue sometimes rents scenery and costumes, but this is a brand new production — and a winner from stem to stern.

Misha Berson: mberson@seattletimes.com