Colonel Zachary Stanley Bayly, CMG (1841–1916) was a South African colonial military commander.
In 1878, he transferred to the colony's new Defence Department, as staff officer responsible for units in Cape Town.
He briefly commanded the city's senior regiment, the Duke of Edinburgh's Own Volunteer Rifles.
In 1879, he transferred to the Cape Mounted Riflemen, and commanded operations in the Morosi campaign that year.
Col Bayly served as Commandant-General of the Cape Colonial Forces from 1882 until he retired in 1892.