Roki Sasaki (Japanese: 佐々木 朗希, Hepburn: Sasaki Rōki, born November 3, 2001), nicknamed "the Monster of the Reiwa Era" (令和の怪物, Reiwa no Kaibutsu), is a Japanese professional baseball pitcher for the Los Angeles Dodgers of Major League Baseball (MLB).

Taking care to avoid subjecting their rookie to premature physical stresses, the Marines held back until the 2021 season before allowing him to make his NPB debut.

His father and grandparents died, while Sasaki, his mother, and his two brothers had to live in a nursing home during the recovery.

[16] For the 2021 season, Sasaki had a 3–2 win–loss record, a 2.27 earned run average (ERA), and 68 strikeouts in 63+1⁄3 innings pitched across 11 appearances.

[4][17] Sasaki made his postseason debut for the Marines in the 2021 Pacific League Climax Series, striking out 10 batters while allowing one run in six innings, as Lotte defeated the Tohoku Rakuten Golden Eagles.

[19] This also became a new world record, beating out the 10 consecutive strikeouts achieved in MLB by Corbin Burnes, Tom Seaver, and Aaron Nola.

He recorded 14 strikeouts on 102 pitches, including striking out the side in the eighth inning with a 101 mph fastball.

[26] On November 8, 2024, the Marines posted Sasaki to allow him to pursue an opportunity with Major League Baseball.

[32] He made his first start of the competition on March 11 against the Czech Republic, pitching 3+2⁄3 innings while giving up two hits, an unearned run, two walks, and recording eight strikeouts.

[33] On March 20, he started in Japan's WBC semifinal game against Mexico, pitching for four innings while giving up five hits, three runs, and recording three strikeouts.

[34] He finished the tournament at 1–0 with a 3.52 ERA and 11 strikeouts across 7+2⁄3 innings, receiving a gold medal in Japan's championship victory over the United States.