The Jack Lynch Tunnel is an immersed tube tunnel and an integral part of the N40 road network in Cork, Ireland. It is named after former Taoiseach, Jack Lynch, a native of Cork.

The N40 road is a national primary road in Cork City, Ireland. It is partial ring road skirting the southern suburbs of the city, from the N22 west of Ballincollig, via the Jack Lynch Tunnel under the River Lee, to the Dunkettle Interchange where it meets the N25 and N8/M8. The present N40 designation was created on 23 February 2012 via statutory instrument by renaming parts of the N22 and N25. The N40 serves as both a commuter route and a bypass of the city centre for traffic between parts southwest and east. The National Transport Strategy envisages building a "Cork North Ring Road" to complete the circuit in the 2030s.