The Lanka Sama Samaja Party (LSSP) was founded in Ceylon (now Sri Lanka) on December 18, 1935, by a group of socialist activists disillusioned with the prevailing political conditions and the lack of representation for workers. Among the founding members were prominent political figures such as N. M. Perera, Philip Gunawardena, and a host of trade union leaders who believed that a dedicated political party was essential for addressing the socio-economic issues faced by the working class. The LSSP's establishment coincided with a period of significant political awakening across colonial Asia, where increasing discontent was simmering under the surface due to oppressive economic policies and lack of civil rights. The founders were inspired by socialist movements across the world, particularly those in Europe, and they sought to adapt these ideas to the local context of Ceylon.

The LSSP quickly emerged as a galvanizing force advocating for social justice, workers' rights, and national independence from British colonial rule. The party initially took a leftist stance, emphasizing the importance of self-determination, land reform, and workers' rights. It engaged actively in labor unions and workers' struggles while promoting policies aimed at improving the living conditions of the proletariat. Their campaign was important for raising political consciousness among the masses and providing them a platform to voice their grievances against the colonial administration. Over time, the LSSP played a crucial role in the broader independence struggle of Ceylon, becoming a pioneering political party that bridged the gap between socialism and nationalism in the country.

Furthermore, as the political landscape evolved, the LSSP adapted its policies and strategies to remain relevant. It was instrumental in building alliances with other leftist and nationalist groups while solidifying its influence by participating in elections, which advocated for broad social and economic reforms. The party's focus on issues such as estate workers' rights, education, and healthcare helped shape the political discourse and policy decisions in a newly independent Sri Lanka decades later.