Hailing from the outer fringes of the Mutter’s Spiral, Ogrons are tall, ape-like humanoids of limited intelligence. Due to their great strength and mindless obedience, they are typically used by other species as mercenaries.
The most common employer of Ogrons were the Daleks. In Day of the Daleks, they used Ogrons to control the human population after their 22nd-century invasion of Earth.
The Daleks also allowed the renegade Time Lord, the Master, to employ the Ogrons when he tried to provoke war between 26th-century Earth and the Draconian Empire in Frontier in Space. This would have made the Daleks the conquerors of the galaxy, but for the intervention of the Third Doctor.