Harbour limits describe the legal limits within which companies may be formed with respect to geographical location of a harbour. That is, a company the harbour of which is situate in the pilotage district of a pilotage authority shall organise and ensure the provision of pilotage services in that pilotage district. Pilotage can be interpreted as the regulations governing the use of a harbour or any docks. The Government of Ireland ratified into law the Harbours Act in 1996, which contains explicit guidance on the stipulations of each harbour in the Republic of Ireland. All harbour and pilotage limits described in http://www.irishstatutebook.ie/eli/1996/act/11/schedule/3/enacted/en/html#sched3 have been digitized, with confirmation sought from local harbours. For each port listed in the National Ports Policy (https://assets.gov.ie/11557/277d22d364fe4c13be390493282c0557.PDF), legislation was sought out describing both the harbour and pilotage district limits of each port. Harbour and pilotage district limits were digitized with reference to the legislation as described in the Harbours Act (1996), and subsequent amendments. Once digitized, all ports were contacted for additional input and validation. This dataset contains the harbour and pilotage district limits for ports listed in the National Ports Policy only where their limits were described within the legislation. While all ports were contacted for validation, only a subset of these ports replied. A summary table of the included ports, limits, legislation source, and validation status has been included below. None