Ehud was the only judge whom the Bible explicitly describes as left-handed.
In Judges 3:15, Ehud is introduced as the son of Gera, a Benjaminite whom God raised up to deliver Israel from oppression by Eglon, king of Moab. The original Hebrew phrase can be understood literally as “restricted in his right hand,” an idiom commonly interpreted as left-handed.
Ehud’s handedness becomes important to the story. He made a short, double-edged sword and strapped it to his right thigh, beneath his clothing. Guards likely expected a conventional right-handed warrior to carry a weapon on the left side, so Ehud was able to enter Eglon’s private chamber with the weapon concealed. He then used his left hand to draw it and kill the Moabite king.
Ehud is generally counted as the second judge of Israel, after Othniel. The Bible mentions other left-handed warriors among the Benjaminites—Judges 20:16 refers to 700 skilled left-handed slingers—but it does not identify them as judges. That distinction is why Ehud is the canonical answer to this trivia question.