Filemon Castelar Lagman, popularly known as Ka Popoy, was a revolutionary socialist and workers' leader in the Philippines who supported Marxism-Leninism. He split with the Communist Party of the Philippines in 1991 due to ideological disagreements to form Bukluran ng Manggagawang Pilipino (BMP). He was assassinated in 2001.

The Bukluran ng Manggagawang Pilipino or Solidarity of Filipino Workers (BMP) is a socialist political center of militant workers and trade unions in the Philippines. It comprises 200 local unions nationwide with a mass membership of over 100,000 laborers.