Elektra, Op. 58, is a one-act opera by Richard Strauss, to a German-language libretto by Hugo von Hofmannsthal, which he adapted from his 1903 drama Elektra. The opera was the first of many collaborations between Strauss and Hofmannsthal. It was first performed at the Dresden State Opera on January 25, 1909.

Elektra is musically complex and difficult, and requires great stamina for the singers and orchestra. The role of Elektra is one of the most demanding in the dramatic soprano repertoire.

Despite being based on ancient Greek mythology, the opera is highly modernist and expressionist. Hofmannsthal and Strauss's adaptation of the story focuses tightly on Elektra, thoroughly developing her character by single-mindedly expressing her emotions and psychology as she meets with other characters mostly one at a time. The other characters are Klytaemnestra, Elektra's mother and murderer of Agamemnon, Elektra's father; her brother Orestes; and her sister Chrysothemis. All three show little development and are secondary to the story. Everything else from the ancient story is minimized as background to Elektra's character and her obsession. Other aspects of the ancient story are completely excluded, tightening the focus on Elektra's furious lust for revenge. The result is a very modern, expressionistic retelling of the ancient Greek myth. Compared to Sophocles's Electra, the opera presents raw, brutal, violent, and bloodthirsty horror.

After the sacrifice of Iphigenia on the ruse that she is to be married, Klytaemnestra has come to hate her husband Agamemnon, who goes off to war against Troy. After his return, with the help of her paramour Aegisth, she murders her husband and now is afraid that her crime will be avenged by her other children, Elektra, Chrysothemis and their banished brother Orest. Elektra has managed to send her brother away while remaining behind to keep her father's memory alive, but all the while, suffering the scorn of her mother and the entire court.

Five servants try to wash the courtyard of the Palace in Mycenae. While they do their work, they ask where can Elektra be, and she emerges from the shadows with a wild look on her face. The servants continue commenting how she came to be in that state and talk about how they taunt her only to receive insults from her. Only one servant shows mercy for her, but she is taken away by the overseer to be flogged.

Elektra comes back for her daily ritual in memory of her father, who, upon his return from Troy and while he was bathing, was killed by Klytaemnestra and Aegisth and dragged out into the courtyard. Elektra now starts imagining the day when her father will be avenged and then of the ensuing celebration in which she will lead the triumphal dance.

Chrysothemis leaves the Palace but, unlike Elektra, she is more meek and accommodating and has remained on good terms with Klytaemnestra and Aegisth, all the time enjoying the privileges inherent to a Princess. She wants to warn her sister that their mother plans to lock Elektra in a tower, but she is rebuffed. Chrysothemis does not wish to go on living a half-death in her own house: she wants to leave, marry and raise children. As loud sounds are heard inside, Elektra mocks her sister that it is her wedding party. In reality, Klytaemnestra has yet again been awakened by her own nightmares of being killed by Orest. Chrysothemis begs Elektra to leave, wishing only to speak to her mother. Followed by a retinue, Klytaemnestra comes to make another sacrifice to appease the gods, but she stops at the sight of Elektra and wishes that she were not there to disturb her. She asks the gods for the reason for her burdens, but Elektra appeases her by telling her mother that she is a goddess herself. Despite the protests of a train bearer and a faithful slave, Klytaemnestra climbs down to talk to Elektra.

Klytaemnestra confides to her daughter that she has been suffering nightmares every night and that she still has not found the way to appease the gods. But, she claims, once that happens, she will be able to sleep again. Coyly Elektra teases her mother with little pieces of information about the right victim that must be slain, but she changes the conversation to her brother and why he is not allowed back. Much to Elektra’s horror, Klytaemnestra says that he has become mad and keeps company with animals. She responds that this is not true and that all the gold that her mother has sent was not being used to support her son but to have him killed.

Then Elektra reveals who is to be the actual victim: it is Klytaemnestra herself. She describes how the gods must be appeased once and for all. She must be awakened and chased around the house just like a hunted animal. Only when she wishes that all was over and after envying prisoners in their cells, she will come to realize that her prison is her body. The opera continues from here.