The Lanka Sama Samaja Party (Revolutionary) (LSSP(R)) was a splinter group of the Lanka Sama Samaja Party (LSSP), a Trotskyist political party in Sri Lanka. It emerged following the LSSP's decision to enter into a coalition government with the Sri Lanka Freedom Party (SLFP) in 1964. This decision was highly controversial within the LSSP, as it was seen as a betrayal of the party's revolutionary principles and an accommodation with bourgeois nationalism.
The LSSP(R) was formed by those members of the LSSP who opposed the coalition, primarily on ideological grounds. They argued that the LSSP's participation in a government led by the SLFP would compromise its socialist aims and ultimately serve to reinforce the capitalist system. The LSSP(R) sought to remain true to the original Trotskyist principles of the LSSP and advocated for a socialist revolution to overthrow the existing government.
Key figures associated with the LSSP(R) included Edmund Samarakkody. The party generally maintained a more orthodox Trotskyist stance than the parent LSSP.
The LSSP(R) participated in elections, but its electoral support was limited. Over time, the party's influence diminished, and it eventually fragmented into smaller groups or individuals reintegrated into other leftist parties. The LSSP(R)'s historical significance lies in its representation of the opposition to the LSSP's coalition politics and its attempt to uphold a more revolutionary socialist perspective within the Sri Lankan political landscape.