The Social Democratic Party of Romania (Romanian: Partidul Social Democrat din România, or Partidul Social Democrat, PSD) was a Marxist social-democratic political party in Romania. A member of the Second International, the party was active between 1910 and 1916, when it was banned. Clandestine groups continued underground activity until 1918, when the end of World War I allowed the party to re-emerge as a legal political group, rechristened Socialist Party of Romania.