Crown Prince Mirko of Monteblanco and his cousin and second-in-line to the throne Prince Danilo Petrovich (Gilbert) stop at an inn along with their traveling party. Also stopping at the inn is the "Manhattan Follies", a traveling theatrical troupe starring dancer Sally O'Hara (Murray). Everybody is drawn to the lovely Sally—Prince Mirko, Prince Danilo, and Baron Sadoja, the richest man in Monteblanco. The thoroughly evil Prince Mirko just wants sex with Sally, and Danilo for his part is almost as predatory, but after Sally recoils when Danilo sets her up for a tryst, he has an attack of conscience. Soon enough they fall in love and Danilo wants to marry Sally. However, the King forbids it. A heartbroken Sally settles for Baron Sadoja, and when he croaks, she inherits all his money and becomes the Merry Widow. This inspires the slimy Mirko to marry her and bring her fortune back into the country. Soon Mirko, Danilo, and Sally all meet again in Paris, and complications ensue.
Like every other film Erich von Stroheim ever directed, The Merry Widow was a Troubled Production. Stroheim clashed with MGM, which actually went so far as to offer him a cash bonus to finish the film on time, only for Stroheim to ignore the studio and go over budget as usual. The studio also forced von Stroheim to adopt a Happy Ending that he hated. Additionally, Stroheim clashed with Mae Murray, as Stroheim hated using established stars and Murray hated the overt sexuality of Stroheim's movie. Despite all of this, The Merry Widow became by far von Stroheim's biggest commercial hit, and helped establish John Gilbert as one of the biggest stars in Hollywood.
Loosely based on the famous 1905 opera by Franz Lehár, which was later loosely adapted into a 1934 musical directed by Ernst Lubitsch. While both films take major liberties with the plot of the opera, this film further departs from the source by being a romantic drama as opposed to a light comedy. Two future huge movie stars, Joan Crawford and Clark Gable, were both extras in the ballroom dancing scene.
- Aside Glance: Right at the end, as Danilo and Sally are walking down the aisle following their coronation and she is gazing up at him adoringly, John Gilbert shoots a quick, cheerful glance right at the camera.
- Awesome Moment of Crowning: The film ends with the coronation of Danilo and Sally as King and Queen.
- The Casanova: Mirko describes Danilo as "an unscrupulous destroyer of womanhood", and judging by how Danilo works to get into Sally's pants, it's true, although he later turns over a new leaf.
- Deus ex Machina / In the Back / Laser-Guided Karma: Mirko has become king, and is marching in his father's funeral procession, when he's murdered, shot in the back by a random assassin.
- Duel to the Death: Mirko and Danilo have one after Mirko's sneering comments about marrying Sally goad Danilo into attacking him.
- Fanservice Extra: Watch out for the topless dancing girls that dine with Danilo and company in a Paris nightclub, as well as the half-naked (and blindfolded!) musicians playing mood music in the brothel where Danilo tries to seduce Sally.
- Fetish: The character of Baron Sadoja has to be the most overt portrayal of foot fetishism in motion pictures, at least until The Hays Code era ended in The '60s. The most notable instance is one scene that features a montage of all the dancers' feet, followed by a shot of Sadoja staring at them with a look of orgasmic glee on his face.
- Footsie Under the Table: Mirko and Danilo try to play footsie with Sally from opposite sides, so she pulls her feet up, and they wind up playing footsie with each other.
- For the Evulz: Mirko beats up an old man on crutches for no damn reason.
- Fourth-Date Marriage: By the end of their first night together, Danilo has asked Sally to marry him.
- Happy Ending: Apparently imposed on von Stroheim by the studio. The previously established Improbable Aiming Skills of Crown Prince Mirko, plus the fact that he had time to take careful aim, do make the idea that Danilo could have survived very unlikely.
- High-Class Glass: Crown Prince Mirko wears one, because he's a douchebag.
- Improbable Aiming Skills: Even while drunk, Mirko can shoot out a cigarette someone's smoking or shoot out both eyes of a statue. This makes the ending pretty unlikely.
- Lingerie Scene: Sally wears a transparent peignoir for her wedding night with Sadoja.
- Male Gaze: Hilariously lampshaded when Sadoja, Mirko, and Danilo are all watching through opera glasses as Sally dances in the show. Sadoja focuses on her feet, cut to Mirko focusing on her curvy torso, cut to Danilo focusing on her face.
- Out with a Bang: Sort of. Sally is sitting on the bed in a transparent peignoir, clearly dreading the sex that is about to come. Sadoja enters, caresses her, and promptly has a fatal heart attack.
- Ruritania: Monteblanco, which judging from the Cyrillic lettering everywhere has to be somewhere in Eastern Europe.
- Sexy Backless Outfit: Sally wears one for the fancy ball in the latter portion of the film.
- Slasher Smile: Crown Prince Mirko spends the whole damn movie with his mouth fixed in an unsettling rictus of a grin.
- Splash of Color: When the film was released, the coronation scene at the end was shot in early Technicolor. Sadly, the color footage has been lost and the surviving ending is in black and white.
- Title Drop: Sally is describe as the Merry Widow after she moves to Paris to live it up.
- Trophy Wife: This is the explicit deal when Sally marries Sadoja, complete with Sadoja's offer that not only will she get money and power, she'll get the social status that will allow her to embarrass the royal family.
- Uptown Girl: Uptown Guy, actually. The King and Queen refuse to allow their nephew to marry a showgirl, and Danilo caves to their pressure.
- You All Meet in an Inn: The film starts with Danilo, Mirko, and Sally all meeting each other at an inn.