Kouyoumdjian or Kouyoumjian (Armenian: Գույումճեան) is an Armenian surname. Notable people with the surname include:
- Dikran Sarkis Kouyoumdjian (1895–1956), later known as Michael Arlen, short story writer and novelist
- Juan Kouyoumdjian, Argentine naval architect
- Ohannes Kouyoumdjian (1852–1933), Ottoman Armenian official
- Robert Kouyoumjian (1923–2011), American electrical engineer and professor emeritus at Ohio State University
- Zaven Kouyoumdjian (born 1970), Lebanese talk show host