The Red Deer is the largest land mammal to be found in Scotland, and is the 3rd largest deer species in the world (only the moose and elk / wapti are larger). Red Deer stags stand around 1.2 metres (4 ft) tall and weigh approx 120kg. Their coats in summer tend to be reddish-brown. The male deer of the British Isles tend to have neck manes. Red Deer hinds (females) do not have neck manes. Red deer in Scotland were originally forest-dwellers but as the forests receded, the deer have adapted and are now generally found in empty glens and moorlands, and roaming the mountain sides.

Only the stags have antlers which start growing in the spring from the age of 10 months. The antlers are shed each year, usually at the end of winter. Antlers are made of bone which can grow at a rate of 2.5cm (1 inch) a day. A soft covering known as velvet helps to protect newly forming antlers in the spring. The antlers are testosterone driven and as the stag's testosterone levels drop in the autumn, the velvet is shed and the antlers stop growing. Antlers can be as long as 140cm and can have up to 12 branches on each antler. Antlers become progressively more branched with age. Shed antlers are chewed by red deer as a source of phosphorous and calcium, so it is best to leave any shed antlers that you may find in the Scottish hills.

During the autumn, Red Deer grow a thicker coat of hair which helps to insulate them during the winter. The winter coat is a greyish-brown coat with a darker yellowish rump patch. By the time summer begins, the heavy winter coat has been shed - the animals often rub against trees to help remove hair from their bodies.