A cotton cultivar, designated PHY 800 Pima, is disclosed. The invention relates to the seeds of cotton cultivar PHY 800 Pima, to the plants and plant parts of cotton cultivar PHY 800 Pima and to methods for producing a cotton plant produced by crossing the cultivar PHY 800 Pima with itself or another cotton variety. The invention further relates to hybrid cotton seeds and plants produced by crossing the cultivar PHY 800 Pima with another cotton cultivar.