Marumi kumquat is Citrus japonica; it is indigenous to Japan and has orangelike fruits that are about 2.5 cm in diameter.

Marumi is the Mame or Hime kinkan of Japan.  In comparison with the Nagami kumquat, which it closely resembles, the fruit of this kumquat is round or slightly oblate, oblate, sometimes obovate, and smaller. The rind is thinner and somewhat sweeter, golden-yellow smooth with a wider range in the number of segments (four to seven) and 1 to 3 seeds, which are smaller than those of Nagami. The tree is less vigorous and somewhat thorny, with smaller, less sharply pointed leaves.  It is considerably more cold tolerant than Nagami and bears at the same season, from October to January.

The Round kumquat was fully described for the first time in 1784. It was introduced to Florida from Japan by Glen St. Mary and Royal Palm nurseries in 1885.