The Partido Demokratiko Sosyalista ng Pilipinas (PDSP), also known as Philippine Democratic Socialist Party, is a political party in the Philippines. It is one of the member parties that composed the United Nationalist Democratic Organization (UNIDO) that supported the candidacy of Corazon Aquino and Salvador Laurel in the 1986 Snap Elections against President Ferdinand Marcos.

In the year 2000, the PDSP mobilized with civil society organizations and groups in support of the impeachment, which led to eventual removal of former President Joseph Estrada from office.

Established on May 1, 1973, the PDSP played a leading role in the difficult task of establishing and expanding a progressive and democratic alternative to the Marcos dictatorship and to Marxism-Leninism. It made an important contribution to the mass campaigns which eventually led to the People Power revolution in 1986.

The PDSP then helped much to consolidate the newly restored democracy, especially through education and mobilization among the small farmers and fisherfolk, workers, urban poor, women, youth, Bangsamoro, and the indigenous peoples of Luzon, Visayas and Mindanao.

The PDSP, mainly through its members in people's organizations and non-government organizations, has helped much to draft laws and government regulations, especially in relation to issues and concerns of farmers, fishermen, workers, urban poor, women, and other sectors of Philippine society.

The Party was accredited by the Commission on Elections (COMELEC) as a legitimate political party in 1990.

In 1992, the party became a consultative member of the Socialist International (SI). In 2019, the PDSP was granted full member status in the SI.^[2]

Starting in 1996, the PDSP actively participated in the interfaith dialogues held between Christian and Muslim groups in the Philippines. These series of events led to the formation of the Bishops Ulama Conference^[3] (BUC) with Romeo Intengan, S.J. and Dr. Mahid M. Mutilan.^[4]

As a social democratic party, the PDSP participates in the political processes of the state,^[9] insisting on elections as a legitimate and viable means of achieving socialism.^[10] It opposes taking the extralegal route preferred and deemed necessary by Marxist–Leninist–Maoist national democrats.^[11]

According to their party platform, they affirm the vision for a first world Philippines and had released a document titled Building a New Philippines. Good politics and governance can provide the foundation for an upright, disciplined and prosperous country. The document is summarised into three major points:

• the social initiative of like-minded groups and organizations to actively contribute in discussions and fora;
• a new breed of leaders that cultivate others and lead by example: patriots imbued and guided by a deep sense of nationalism; and
• a program of developing the country economically, politically and culturally.

As such, the party holds thirteen principles:

• the human being as an embodied spirit or a psychocorporeal being;
• the human being's normal capacity for personhood, entailing ethical responsibility, rights and duties;
• the essential equality of human beings;
• the social nature of human beings and the state as a natural institution;
• the principle of subsidiarity;
• preferential option for the poor and marginalized;
• work as a right and duty of human beings;
• the obligation to patriotism;
• the rights of nations;
• the universal purpose of property or custodianship for the common good;
• the transcendent moral responsibility of human beings and the primacy of moral law;
• the moral ambivalence of human persons;^{[further explanation needed]} and
• the abuse of power in all fields of human activity as the real structural origin of alienation.