| Engelberger Aa | |
|---|---|
| Origin | West of Surenenpass |
| Mouth | Lake Lucerne |
| Basin countries | Switzerland |
| Length | 50 km |
| Mouth elevation | 433 m |
| Basin area | 230 km² |
Engelberger Aa (or Engelbergeraa) is a river in Switzerland. It rises west of Surenenpass in the Canton of Uri, flows through the valley of Engelberg (Obwalden) and Nidwalden. At Buochs, it empties into Lake Lucerne. It is a tributary of the river Reuss.