Saul Wahl Katzenellenbogen (1541–1617) was a wealthy and politically influential Polish Jew who is said to have briefly occupied the throne of Poland and thus has historically borne the nickname, "Le roi du jour" (king for a day). Jewish historians maintain that that day was August 18, 1587. Wahl had thirteen children, including the renowned Polish rabbi, Meir Wahl Katzenellenbogen.
Saul's father was Samuel Judah Katzenellenbogen.
The story that Saul was briefly king of Poland is rejected by historiographers because there is no physical evidence to prove its veracity one way or the other, but it has gained a firm place in the folklore of the Jewish people.
The version of the story set forth in the Jewish Encyclopedia reads as follows:
"At a point in his life, Lithuanian noble Mikołaj Krzysztof "the Orphan" Radziwiłł (1549–1616) wished to repent for the numerous sins he had committed when he was younger. He commenced a pilgrimage to Rome in order to consult the pope as to the best means for the propitiation of his misdeeds. The pope advised him to dismiss all his servants and to live for a few years as a wandering beggar. When the prescribed period ended, Radziwill was penniless in the city of Padua, Italy. He pleaded for help, but his claims of being a noble fell on deaf ears.
Radziwiłł decided to appeal to Samuel Judah Katzenellenbogen, the rabbi of Padua. Katzenellenbogen treated him kindly and provided him with the means to return to Lithuania. To allow Radziwiłł to repay the favor, Shmuel asked that he help find his son Saul, who years before had left to study in a yeshiva in Poland. When Radziwiłł visited Poland, he inquired at all yeshivas until he found Saul in Brest-Litovsk (now Brest, Belarus).
Radziwiłł was impressed with Saul's intellect and offered to board (feed) him in his own castle, where Saul could pursue his studies. Radziwill's court personnel were similarly impressed with Saul, and his reputation spread throughout Poland.
Stephen Báthory, who was king of Poland, died in 1586, and the Poles were divided between wishing to be ruled by the Zamoyski family and the Zborowski family. Polish law at that time stated that if electors could not agree upon a king, an outsider should be appointed "rex pro tempore" (temporary king). Radziwill proposed that Saul Wahl Katzenellenbogen be appointed temporary king, and Wahl was elected to shouts of "Long live King Saul!"
Estimates of the duration of Saul's reign range from one night to a few days, yet Wahl passed numerous laws, including laws that improved conditions for Polish Jews. The name "Wahl" was thus appended to his name; it derives from the German word Wahl meaning "election".
Historian Gustav Karpeles writes that "an historical kernel lies hidden in the legend" that, he says, "rests upon an historical substratum". Mikołaj Krzysztof "the Orphan" Radziwiłł, he says, made a widely publicized pilgrimage to Jerusalem. While returning, wrote Radziwiłł, he was attacked in Italy by robbers and was left in Ancona without any money. His pleas for help were ignored by all except a Jewish merchant, who alone believed his claim that he was a Polish noble. The merchant provided him with funds to return to Poland. Karpeles concludes that Radziwiłł's narrative is consistent with the narrative of the Jewish tale and that the lone Jewish merchant who had helped Radziwiłł was Samuel Judah Katzenellenbogen, Saul Wahl's father.