Begonia rajah is one of the most ornamental species of the genus Begonia. It is native to the Malaysian peninsula where it grows on rocks along streams. In cultivation it is usually grown in a terrarium in a sphagnum moss perlite mix or in a good loose potting soil mix. It will also grow in a humid greenhouse. It has a rhizomatous growth habit. The leaves are kidney shaped with a pointed tip. The leaf surface is light green with raised mahogany colored areas between the veins. The flowers are small, light pink to white.