Uisce Éireann (/ˈɪʃkə/ ISH-kuh /ˈɛərən/AIR-un, Irish: [ˈɪʃkə ˈeːɾˠən̪ˠ]), formerly known as Irish Water, is a state-owned water utility company in Ireland. It was created by the Irish Government in 2013 as a subsidiary of Bord Gáis. Water and wastewater services were previously provided by local authorities in Ireland. The company was renamed Uisce Éireann on 31 December 2022. The renaming was done a day before the company was split from its former parent body Ervia. From 1 January 2023 the company became a standalone national utility for water services.

The organisation is accountable to two regulatory bodies, the Commission for Regulation of Utilities (CRU) which is the economic regulator for the water industry, and the Environmental Protection Agency (EPA) which is the environmental regulator.

Water supply and sanitation in Ireland are governed by the Water Services Acts of 2007 to 2014. Until 2015, this legislation provided for the provision of water and wastewater services by local authorities, with domestic usage funded through central taxation, and non-domestic usage funded via local authority rates.

In 2013, Uisce Éireann (known until 2022 as Irish Water) was established under the Water Services Act 2013, which created the company as a subsidiary company of Bord Gáis. to provide "safe, clean and affordable water and waste water services" to water users in the country. Under terms of a 2010 Economic Adjustment (Bailout) Programme, the then government agreed to change this arrangement. From 2015, legislation came into force such that Uisce Éireann became responsible for providing water and wastewater services, with the intention that the company would be funded through direct billing. The new company was set up as a subsidiary of an existing semi-state corporation, Bord Gáis (Ervia). The newly created company effectively took on the existing local authority employees and water management facilities, pipes and infrastructure. Operationally, Uisce Éireann delegates some work, for example water meter installation and customer support, to sub-contractors.

Public concerns on operational, documentation, company responsiveness, data security, financial and perceived wasteful spending issues were highlighted throughout the initial months of Uisce Éireann's operations. Together with privatisation fears, these public concerns resulted in a significant volume of unreturned application forms, large nationwide protests and pressure on company management and the government during 2014. In 2015, the scale of non-payment issues, and an unfavourable assessment of the viability of the organisation as an independent entity further increased attention and calls by some to dissolve the organisation. The viability of the utility was also a feature ahead of the 2016 general election, and post-election discussions on government formation.

Uisce Éireann is responsible for the maintenance and repair of Ireland's water supply infrastructure. It has also been tasked with refurbishing the water supply, including addressing leaks and replacing old infrastructure,, and with ensuring an adequate water supply for Ireland's growing population.

In July 2022, it was announced that the company would be renamed from Irish Water to Uisce Éireann as part of a split from its parent body Ervia. This took effect from 1 January 2023.

The company has been the subject of several civil cases, including one taken by Crohn's Disease sufferer Elizabeth Hourihane, and one taken by the Environmental Protection Agency (EPA) which initiated proceedings over the standard of water in County Donegal.