The Robin is a plump bird with bright orange-red breast, face, throat and cheeks edged with grey, a white belly and olive-brown upper parts. The sexes are very similar, if not identical, though some texts suggest that the brown forehead is "V" shaped in females, and "U" shaped in males, though even this is not always apparent. They have a brown bill and legs.

The juvenile Robin has speckled buff-brown upper parts and underparts. They have no red feathers so that adult birds do not attack them in territorial disputes. The speckled feathers are lost in a partial moult when the bird is about two to three months old.

In the winter, resident birds are joined by immigrants from continental Europe, mostly from Scandinavia; these Robins are paler than ours, and have a duller red breast. The immigrants are also generally less tame because they skulk in woodlands, only British Robins are a tame garden bird. Robins are territorial all year round; during the spring and summer this territoriality is for breeding, but at other times individual robins hold territories for feeding. Robins will defend their territories to the death