Norma, dagger in hand, tries to bring herself to murder her children in their sleep to protect them from living disgracefully without a father. She cannot and instead summons Adalgisa begging her to marry Pollione and take the children to Rome. Adalgisa refuses: She will go to Pollione but only to persuade him to return to Norma. Overcome by emotion, Norma embraces her, and the women reaffirm their friendship.

The warriors assemble in the forest to hear Oroveso’s announcement that a new commander will replace Pollione. Oroveso rages against the Roman oppression, but tells them that they must be patient to ensure the success of the eventual revolt.

Norma is stunned to hear from Clotilde that Adalgisa’s pleas have not persuaded Pollione to return to her, and, in a rage, she urges her people to attack the conquerors. Oroveso demands a sacrificial victim. Just then, Pollione is brought in, having profaned the druids’ sanctuary. Alone with him, Norma promises him his freedom if he will give up Adalgisa for her. When he refuses, Norma threatens to kill both their children and Adalgisa to punish him. But when she calls in the druids and tells them that a guilty priestess must die, she confesses that she is referring to herself. Moved by her nobility, Pollione asks to share her fate. Norma begs Oroveso to watch over her children, then leads her lover to the pyre.