Calamansi (Citrus × microcarpa), also known as calamondin, Philippine lime, or Philippine lemon, is a citrus hybrid cultivated predominantly in the Philippines. It is native to the Philippines; extending southwards to nearby parts of Indonesia (Borneo, Sumatra, and Sulawesi), Malaysia, and Brunei; and northwards to Taiwan and tropical regions of southern China (mainly Hainan).

Calamansi is ubiquitous in traditional Philippine cuisine. It is naturally very sour, and is used in various condiments, beverages, dishes, marinades, and preserves. Calamansi is also used as an ingredient in Malaysian and Indonesian cuisines.

Calamansi is a hybrid between kumquat (formerly considered as belonging to a separate genus Fortunella) and another species of Citrus (in this case probably the mandarin orange).