Lady Gaga has traveled by egg, donned skirt steak and taken part in a TV blood orgy. But her biggest transformation occurs in the new film “A Star Is Born.” In it, she becomes an Oscar-worthy actress.

Taking on the classic part of a talented unknown who rises to music superstardom — the iconic role that Janet Gaynor, Judy Garland and Barbra Streisand played before her — Gaga proves her acting chops by trading in flash for humanity.

You won’t believe she’s the same person who once sang the lyric “I wanna take a ride on your disco stick.” And you will be downright shocked that this electrifying film is the third remake of “A Star Is Born.”

The previous rehash of the 1937 original was the chintzy, critically loathed 1976 version starring a soupy Streisand. Garland and Gaynor’s earlier turns are classic, but oversized by today’s standards.

Gaga, however, shows brilliant restraint. And for Mother Monster, subtlety is a huge achievement.

She plays Ally, a waitress at a high-end restaurant who hates her job and is frustrated with her stagnant life. Ally’s passion is singing, which she gets to do at a local drag bar at night.

During one fortuitous set, famous rocker Jackson Maine (Bradley Cooper) stumbles in drunk. On the hunt for another bottle, he ends up transfixed by Ally’s rendition of “La Vie En Rose” and the pair stay up all night, flirting.

Jackson flies her out to his concert the next day and she unexpectedly croons an original song with him onstage. The moment becomes a viral YouTube sensation and a whirlwind romance begins, propelled by a true love of their art, but scarred by easy access to booze and hard drugs. Ally is caught in a bad romance as Jackson succumbs to addiction.

The stripped-down, makeup-free Gaga has chemistry with the equally unrecognizable Cooper. The actor is perfectly charming, and tortured, as Jackson — the affable sort of musician who could always use a shower. Jackson struggles as Ally ascends, and the disintegration of their once-innocent relationship is devastating to watch. Bring the tissues.

Cooper’s voice is strong, too, and you believe that a few million people might actually buy this guy’s CD. He and Gaga sing many original numbers written for the film. They range from soothing barstool ballads to clubby pop tunes, but are united by their genuine feel. They don’t sound like movie music.

“A Star Is Born” also marks Cooper’s first movie as director. Virgin filmmakers tend to either overdo it with weird techniques or go textbook basic. But Cooper delivers his gutsy style with the confidence of a veteran, juxtaposing high-octane, quick-cut concerts with long, pale shots of the couple’s home life.

Most thrilling are the stage sequences. Cooper often films Ally’s thousands of screaming fans from her point of view — putting us in her lucky shoes for a minute.

It’s that feeling of exhilaration that makes “A Star Is Born” the best film of the year so far.