Two new species of Begonia (Begoniaceae), Begonia ozotothrix and Begonia hekensis, are described from the Indonesian island of Sulawesi. Both species belong to Begonia section Petermannia. Begonia ozotothrix is unusual amongst Asian Begonia in having branched trichomes on the stems, petioles and the abaxial lamina surfaces, and it is unusual amongst species of Begonia section Petermannia in having extremely compressed cymose-subumbellate male partial inflorescences.