The film is set in June 1905; the protagonists of the film are the members of the crew of the Potemkin, a battleship of the Imperial Russian Navy's Black Sea Fleet. Eisenstein divided the plot into five acts, each with its own title:
Act I: Men and Maggots
The scene begins with two sailors, Matyushenko and Vakulinchuk, discussing the need for the crew of the Potemkin to support the revolution taking place within Russia. While the Potemkin is anchored off the island of Tendra, off-duty sailors are sleeping in their bunks. As an officer inspects the quarters, he stumbles and takes out his aggression on a sleeping sailor. The ruckus causes Vakulinchuk to awake, and he gives a speech to the men as they come to. Vakulinchuk says, "Comrades! The time has come when we too must speak out. Why wait? All of Russia has risen! Are we to be the last?" The scene cuts to morning above deck, where sailors are remarking on the poor quality of the meat for the crew. The meat appears to be rotten and covered in worms, and the sailors say that "even a dog wouldn't eat this!" The ship's doctor, Smirnov, is called over to inspect the meat by the captain. Rather than worms, the doctor says that the insects are maggots, and they can be washed off prior to cooking. The sailors further complain about the poor quality of the rations, but the doctor declares the meat edible and ends the discussion. Senior officer Giliarovsky forces the sailors still looking over the rotten meat to leave the area, and the cook begins to prepare borscht although he too questions the quality of the meat. The crew refuses to eat the borscht, instead choosing bread and water, and canned goods. While cleaning dishes, one of the sailors sees an inscription on a plate, which reads "give us this day our daily bread." After considering the meaning of this phrase, the sailor smashes the plate and the scene ends.
Act II: Drama on the Deck
All those who refuse the meat are judged guilty of insubordination and are brought to the fore-deck where they receive religious last rites. The sailors are obliged to kneel and a canvas cover is thrown over them as a firing squad marches onto the deck. The First Officer gives the order to fire, but the sailors in the firing squad lower their rifles and the uprising begins. The sailors overwhelm the outnumbered officers and take control of the ship. The officers are thrown overboard, the ship's priest is dragged out of hiding, and finally the doctor is thrown into the ocean as 'food for the fish'.
Act III: A Dead Man Calls for Justice
The mutiny is successful but Vakulinchuk, the charismatic leader of the rebels, is killed. The Potemkin arrives at the port of Odessa. Vakulinchuk's body is taken ashore and displayed publicly by his companions in a tent with a sign on his chest that says "For a spoonful of soup" (Изъ-за ложки борща). The sailors gather to make a final farewell and praise Vakulinchuk as a hero. The people of Odessa welcome the sailors, but they attract the police.
Act IV: The Odessa Steps
The best known sequence of the film is set on the Odessa steps, connecting the waterfront with the central city. A detachment of dismounted Cossacks forms a line at the top of the steps and march towards a crowd of unarmed civilians including women and children. The soldiers halt to fire a volley into the crowd and then continue their impersonal, machine-like advance. Brief sequences show individuals amongst the people fleeing or falling, a baby's pram rolling down the steps, a woman shot in the face, broken spectacles and the high boots of the soldiers moving in unison.
In retaliation, the sailors of the Potemkin decide to fire on a military headquarters with the guns of the battleship. Meanwhile, there is news that a squadron of loyal warships is coming to quell the revolt of Potemkin.
Act V: One against all
The sailors of the Potemkin decide to go all the way and lead the battleship from the port of Odessa to face the fleet of the Tsar. Just when the battle seems inevitable, the sailors of the formerly loyal ships incredibly refuse to open fire on their comrades, externalizing with songs and shouts of joy their solidarity with the mutineers and allowing them to pass unmolested through the fleet, waving the red flag.