Henry IX (died 13 December 1126), called “the Black”, a member of the House of Welf, was duke of Bavaria from 1120 to 1126.

Henry was the second son of Welf I, Duke of Bavaria. As a young man, he administered the family's property south of the Alps. Through his marriage to Wulfhild, daughter of Magnus, Duke of Saxony, he acquired part of the Billung property in Saxony.

In 1116, he joined Emperor Henry V's Italian campaign. He succeeded his brother Welf II, Duke of Bavaria, when the latter died childless in 1120.

In the royal election of 1125, he supported his son-in-law Frederick II, Duke of Swabia, but switched his allegiance to Lothair, Duke of Saxony, after Lothair promised that Gertrud, his only daughter and heir, would marry Henry's son Henry.

After Lothair won the election and banned Frederick, in 1126 Henry stepped back as duke of Bavaria and joined the Monastery of Weingarten so that he did not have to take part in the prosecution of his son-in-law. Henry died shortly thereafter and was buried in Weingarten.

Henry had the following children:
• Judith, married Frederick II, Duke of Swabia
• Conrad, died 17 March 1126
• Henry X the Proud
• Welf
• Sophia, married Berthold III, Duke of Zähringen and Leopold I, Duke of Styria
• Wulfhild, married Rudolf, Count of Bregenz
• Mathilde, married Diepold IV, Margrave of Vohburg and Gebhard III, Count of Sulzbach
• Adalbert, Abbot of Corvey