Oy or OY may refer to:
- Oy vey Oy, a Yiddish exclamation of chagrin, dismay, exasperation or pain
- A village in the Oy-Mittelberg municipality, Bavaria, Germany
- oy (digraph), a digraph found in many languages
- Osakeyhtiö (abbr. Oy), a prefix/postfix indicating a Finnish Limited company
- Oy (Dark Tower), an animal character in Stephen King's Dark Tower series
- Opportunity Youth, a Youth organization in Northern Ireland
- Omni Air International (IATA airline designator)
- "OY" (Oscar, Yankee), the aircraft registration code prefix for airplanes from Denmark
- Oye! (film), a 2009 Telugu film starring Siddharth Narayan and Shamili
- Oy (album), a studio album of Iranian singer-songwriter Mohsen Namjoo
- The code for County Offaly, Ireland
- Oy (archaic Scots), a grandchild Dictionary of the Scots language
- Oy (archaic Scots), a niece or nephew Dictionary of the Scots language
- OY-(three digit number), a code for flights with the former Danish airline company Conair of Scandinavia (1964–1994)