Noctilien is the night bus service in Paris and its agglomeration. It is managed by the Île-de-France Mobilités, the Île-de-France regional public transit authority, and operated by RATP and Transilien SNCF.

Night service, sometimes also known as owl service, is a mode of public transport service operated during the night hours. As an intermediate approach – between providing full service around the clock and stopping services altogether – it provides more limited service during times of lower passenger volume, saving resources and allowing for maintenance on primary transportation systems. They typically offer fewer routes and less frequent service. Night-based services may be differently branded compared to daytime services. Examples are London and Chicago, where overnight buses are prefixed with an "N" for "night". Another common way to distinguish night services from their daytime counterparts is dark-colored line numbers. Some cities apply a different fare structure for night services from their daytime services.