The Westerbach is a right tributary of the Kahl in the northern Spessart in Lower Franconia, Bavaria, Germany.

It is 6.3 km (3.9 mi) long (7.2 km including Querbach) and begins at the confluence of Querbach and Huckelheimer Bach in Westerngrund. The Querbach rises in the Arzborn, a small opening in the mountainside on the Hoher Querberg, northeast of Huckelheim, near the border between Hesse and Bavaria. In Schöllkrippen the Westerbach empties in the Kahl.

Together with Sommerkahl, Reichenbach and Geiselbach, the Westernbach is one of the largest tributaries of the Kahl.

• Querbach (left headstream)
• Huckelheimer Bach (right headstream)
• Hombach (right)
• Schulzengrundbach (left)
• Dörnsenbach (right)
• Herzbach (left)
• Schneppenbach (right)
• Betzenbach (right)

• 
  The Arzborn (Spring of Querbach)
• 
  Between Unterwestern and Schneppenbach

• List of rivers of Bavaria