| State: | LA |
| Type: | LA |
| Route: | 42 |
| Map: | LA 42 map.svg |
| Length Mi: | 47.8 |
| Established: | 1955 renumbering |
| Direction A: | West |
| Terminus A: | in Baton Rouge |
| Junction: | in Baton Rouge in Prairieville |
| Direction B: | East |
| Terminus B: | in Springfield |
| Parishes: | East Baton Rouge, Ascension, Livingston, Tangipahoa |
| Previous Type: | LA |
| Previous Route: | 41 |
| Next Type: | LA |
| Next Route: | 43 |
Louisiana Highway 42 (LA 42) is a state highway in Louisiana that serves East Baton Rouge, Ascension, Livingston, and Tangipahoa parishes. It spans 47.8miles in a general east–west direction.
From the west, LA 42 starts at an intersection with LA 30 in Baton Rouge near Louisiana State University. It is a four-lane divided highway for 7.6miles from LA 30 eastward to an intersection with Highland Road and Siegen Lane in southeastern Baton Rouge. This section is named Burbank Drive.
From this intersection, LA 42 turns east and follows Highland Road to US 61 (Airline Highway). In this segment, it passes the Highland Road Park and Observatory and the Louisiana Country Club. Curving to the northeast, LA 42 widens to four lanes and passes through an interchange with I-10 (exit 166).
LA 42 turns southeast and overlaps US 61 out of East Baton Rouge Parish and into Ascension Parish for 3.3miles. At this point, LA 42 turns eastward and meanders its way across the Amite River and into Livingston Parish, intersecting LA 16 at Port Vincent. For the next 3.1miles, LA 42 and LA 16 run concurrently into the north end of French Settlement. LA 42 proceeds eastward through rural Livingston Parish until reaching its terminus at LA 22 in the town of Springfield. As of 2018, the portion west of US 61 is under agreement to be removed from the state highway system and transferred to local control.[1]