Cornelius Colbert (1888 - May 8, 1916) was an Irish rebel and pioneer of Fianna Eireann. Born in County Limerick, at a young age his family moved to Dublin, and in 1913 he was an early member of the Irish Volunteers, perhaps the youngest member of its Provisional Committee. He also joined the Irish Republican Brotherhood. Soon after Patrick Pearse asked him to be a drill instructor for his St. Enda's School.

In 1916 Colbert took part in the Easter Rising. As captain of F company in the 4th battalion under Commandant Eamonn Ceannt he was in charge of commandeering Watkin's Brewery. When the position proved too large and strategically insignificant he moved the company to the Jameson's Distillery, where he became a de facto commandant. Following the surrender he was court-martialled and executed by firing squad on May 8.

Colbert was a deeply religious Catholic, and refrained from smoking, drinking, and swearing, as well as dancing during Lent.