Leopards were a type of large predatory mammal native to Africa on Earth. They usually had spotted coats like jaguars.
Encounters with leopards
While attempting to hide in a tree from the Quarks, the Second Doctor and Jamie found a leopard already in it. They managed to catapult the leopard out of the tree, giving them time to flee while the Quarks fought with the leopard. (TVC: Jungle of Doom)
The Great Old Ones showed Erimem that her father, prior to his death, had given the order to Pyran that she should be bound and thrown to the leopards on her next birthday. (BFA: The Roof of the World)
Somerset's leopards were a genetically enhanced version of the cat employed for domestic functions. Qixotl created his own kind that could record information that could later be read from their urine. They also consumed people who weren't on his guest list. (EDA: Alien Bodies)
Leopard skin in art
The leopard's spotted pattern was used in clothing and decoration. Iris Wildthyme owned a leopard-skin coat which once surprised her by attacking a magician. (BFIW: Roubh Magic)
The Fifth Doctor considered the coral desktop theme used in the TARDIS by his future incarnation to be worse than the leopard skin theme. (DW: Time Crash)
Cultural references to leopards
The Veiled Leopard was the name of a diamond once owned by Erimem. (BFA: The Veiled Leopard) In western Africa, a group called the leopard society kept secret knowledge of the Great Old Ones. (NA: White Darkness) Red Leopard was a crime family. (BNA: Ghost Devices)