Keiko O'Brien
- Full Name: Keiko O'Brien (née Ishikawa)
- Species: Human
- Gender: Female
- Father: Hiro Ishikawa
- Sister: Midori Ishikawa
- Husband: Miles O'Brien (2367 - Present)
- Married May 23, 2367 (TNG: "Data's Day")
- Daughter: Molly O'Brien
- Son: Kirayoshi O'Brien
- By 2367: Botanist; USS Enterprise (TNG: "Data's Day")
- June 2369: Primary school teacher; Deep Space 9 (DS9: "A Man Alone")
- March 2371: Extended agrobiology expedition, Bajor (DS9: "The House of Quark")
- Early January 2376: Resident; San Francisco, United States of America, Earth (DS9: "What You Leave Behind..."; SCE Short Story: "Aftermath")