1931 in Japanese baseball
 Professional Baseball
 High School Baseball
The 17th National High School Baseball Championship featured a total of 634 schools competing for 22 spots The finals at Koshien. In the championship game Chukyo High School (Aichi) defeated Yoshimi Gi Nourin High School (Taiwan) by a score of 4 - 0.
The 8th National High School Baseball Invitational Tournament featured 19 schools competing in the tournament at Koshien. In the championship game Hiroshima High School (Hiroshima) defeated Chukyo High School (Aichi) by a score of 2 - 1.
 University Baseball
Both the Tohto University Base Ball League and the Kansai 6 University Baseball League began play in the fall.
 Tokyo Big6 Baseball League
The Hosei team toured the United States in the spring and did not participate in the league.
 Tohto University Base Ball League
 Kansai 6 University Baseball League
 International Baseball
The Herb Hunter and Fred Lieb All-Stars toured Japan in 1931. The touring team went 17 - 0 - 0 against Japanese competition.