The Jack Lynch Tunnel (named after former the Taoiseach, Jack Lynch) is an integral part of the N25 southern ring road of Cork in Ireland. It takes the road under the River Lee. North of the tunnel, the ring-road joins the N8 road to Dublin (north), and the city centre (west), with the N25 continuing east to Waterford. The tunnel was completed in 1999, and carries nearly 40,000 vehicles per day as of 2005.

The tunnel transports vehicular traffic in uni-directional bi-lane tunnels. During periods of maintenance the system operates in a bi-directional uni-lane fashion.

The tunnel has footpaths but they are for emergency use only as pedestrians and cyclists are expressly forbidden from using the tunnel. The exclusion of cyclists has been somewhat controversial as the feeder road is only a dual-carrigeway and so is open to cyclists.

Despite the cost of its construction and operation the tunnel is not tolled. But tolls could be introduced in the future on the Northbound bi-lane, which is suitable, having the required space and roundabout free tailback capacity.

See also: Roads in Ireland