A rice cultivar designated Calhikari-203 is disclosed. The invention relates to the seeds of rice cultivar Calhikari-203, to the plants of rice Calhikari-203 and to methods for producing a rice plant produced by crossing the cultivar Calhikari-203 with itself or another rice variety. The invention further relates to methods for producing a rice plant containing in its genetic material one or more transgenes and to the transgenic rice plants and plant parts produced by those methods. This invention also relates to rice cultivars or breeding cultivars and plant parts derived from rice cultivar Calhikari-203, to methods for producing other rice cultivars, lines or plant parts derived from rice cultivar Calhikari-203 and to the rice plants, varieties, and their parts derived from the use of those methods. The invention further relates to hybrid rice seeds and plants produced by crossing the cultivar Calhikari-203 with another rice cultivar.