Fischbach (German pronunciation: [ˈfɪʃˌbax]) is a municipality in the district of Willisau in the canton of Lucerne in Switzerland.

Of the rest of the land, 5.3% is settled (buildings or roads) and the remainder (0.1%) is non-productive (rivers).

Of the settled areas, 3.11% is covered with buildings, 0.25% is classed as special developments, and 1.99% is transportation infrastructure.

The municipality is located in the hill country near the Rot river valley.

Most of the population (as of 2000[update]) speaks German (94.0%), with Albanian being second most common ( 3.8%) and Serbo-Croatian being third ( 0.9%).

The age distribution, as of 2008[update], in Fischbach is; 206 people or 28.8% of the population is 0–19 years old.

In the 2000 census[update] the religious membership of Fischbach was; 475 (70.1%) were Roman Catholic, and 122 (18.%) were Protestant, with an additional 6 (0.88%) that were of some other Christian faith.