"Someday" is a song written by Mariah Carey and Ben Margulies, and produced by Ric Wake for Carey's debut album Mariah Carey (1990). It was released as the album's third single in the first quarter of 1991 (see 1991 in music) and is a jackswing-influenced track in which its protagonist gets revenge on an ex-lover who wants to reconcile: "Someday, the one you gave away will be the only one you're wishing for". Though it topped the U.S. charts, it was not a huge success elsewhere.

"Someday (I Will Understand)" is the first single from Pop singer Britney Spears originally released from the EP/Bonus disc of Britney & Kevin: Chaotic... The DVD & More during the third quarter of 2005, though the song was later included in its Hi-Bias Signature Radio Remix form on the B in the Mix: The Remixes compilation.

"Someday" is a 2003 single by the band Nickelback, the first one from their 2003 album The Long Road. It reached number one in Canada for three weeks and the top ten in the United States.

Someday is a science fiction short story by Isaac Asimov. It was first published in the May 1956 issue of Infinity Science Fiction and reprinted in the collection Earth Is Room Enough.

some unspecified time in the future; "someday you will understand my actions"