Nijinomatsubara (虹之松原, nijinomatsubara) is a 360-year-old pine forest in Karatsu, Saga. It has a width of 400 - 700 metres, a length of about 4 km, and a total area of 240 hectares. It was also referred as The Black Pine Forest of 1 Million Trees (百万本のクロマツを中心とした松林, hyaku man hon no kuromatsu wo chuushin toshita matsubayashi), however this name is uncommon today.

The forest was originally planted by the feudal lord Terazawa Hirotaka as a counter-measure against the strong winds and tides in Karatsu Bay. Today it is a popular tourist spot, and on a list of the 100 most beautiful places in Japan.

This forest is easily accessible from both Karatsu City and Fukuoka City, by the Chikuhi Line. There are several hotels and places to park nearby.