Dong Phaya Yen or Dong Phya Yen is a mountain range in Phetchabun, Chaiyaphum, Lopburi, Saraburi, and Nakhon Ratchasima Provinces, Thailand. As the Dong Phaya Yen is less compact and lower in height than the mountain ranges to the north and to the south, the first roads and railroads connecting the region of Isan with the capital Bangkok were built across these mountains.