Homburg Ruin, Medieval castle ruin in Läufelfingen, Switzerland.

Homburg, also called Neu-Homberg, is a ruined hilltop castle above the narrowest point of the Homburgertal in Läufelfingen. Its main surviving element is a three-story residential tower with walls up to three meters thick, accompanied by outbuildings, a ring wall and gate structures.

The fortress was built in 1240 by Count Hermann IV von Frohburg and served as a residence and administrative center for Basel's regional officials. The structure was burned down by local residents during the French Revolution in 1798.

The castle's name comes from Hermann IV von Frohburg, who called it Neu-Homberg after adopting the name of his wife, heiress of the counts of (Alt-)Homberg in the Fricktal. From 1400 Basel appointed Landvögte who lived in the castle and administered the Amtei Homburg for four centuries, first chosen from the Small Council and later from Basel's citizenry.

Marked trails lead to the ruin from Buckten or Läufelfingen train stations, with a walking time of around thirty minutes from either location. Sturdy footwear is recommended since the route involves uphill walking to reach the site.

The viewing platform sits 8.5 metres up the residential tower, reached by 43 steps, and looks out over Läufelfingen, Buckten and the hills of the Basel Jura. The tower walls below it reach up to three metres in thickness.