A cotton cultivar, designated DP 556 BGII/RR, is disclosed. The invention relates to the seeds of cotton cultivar DP 556 BGII/RR, to the plants of cotton DP 556 BGII/RR and to methods for producing a cotton plant produced by crossing the cultivar DP 556 BGII/RR with itself or another cotton variety. The invention further relates to hybrid cotton seeds and plants produced by crossing the cultivar DP 556 BGII/RR with another cotton cultivar.