Seki-san no mori, Traditional woodland in Matsudo, Japan.

Seki-san no mori is a 2.1-hectare woodland in Kōya, Matsudo, Chiba Prefecture, donated in 1995 by sisters Michiko and Keiko Seki and named after them. It was designated a special conservation forest area by Matsudo City on July 1, 2002. The site includes a yashikirin (farmstead grove), a spring-fed pond, and the adjacent Seki-san no mori farm and children's plaza.

This woodland is a remnant of satoyama, a traditional Japanese land management system that developed over centuries. The system reflects how people historically balanced their needs with environmental stewardship in the Japanese landscape.

The forest takes its name from the Seki sisters, Michiko and Keiko, who owned the roughly 2.1-hectare yashikirin and donated it to the Saitama Prefecture Ecosystem Conservation Association in 1995. They acted as many estate woodlands across Japan were being felled to pay inheritance tax. The name "Seki-san no mori" comes directly from their family name.

The woodland is easily accessible from central Matsudo and offers paths suitable for various walking abilities. Spring and autumn are the best times to visit when temperatures are mild and seasonal plant changes are most visible.

The woodland was donated in 1995 by sisters Michiko and Keiko Seki, whose surname gives the forest its name. The 2.1-hectare site was later designated a Matsudo special conservation forest area in 2002. A roughly 200-year-old Japanese raisin tree was transplanted using a tree-spade method when a new road was built.