The Japan Diamond Softball League (JD.League) is a Japanese women's softball league that consists of 16 teams (8 in the East Division and 8 in the West Division). The league is the premier women's softball league in the country. The league was formed in 2022 and is headquartered in Shinjuku, Tokyo. The JD.League is a member of the , which comprises the top-tier sports leagues in Japan. Nitori entered into the title partnership with the JD.League, and thus the league is officially called as Nitori JD.League.