Sangen (or Sankan) is a general term for the three important sekisho (a checkpoint) out of which were established in and around Kinai (five capital provinces surrounding the ancient capitals of Nara and Kyoto) in ancient Japan.
三関（さんげん、さんかん）とは、古代の日本で畿内周辺に設けられた関所の内、特に重視された三つの関の総称。