County Meath (/miːð/ MEEDH; Irish: Contae na Mí or simply an Mhí, lit. 'middle') is a county in the Eastern and Midland Region of Ireland, within the province of Leinster. It is bordered by County Dublin to the southeast, Louth to the northeast, Kildare to the south, Offaly to the southwest, Westmeath to the west, Cavan to the northwest, and Monaghan to the north. To the east, Meath also borders the Irish Sea along a narrow strip between the rivers Boyne and Delvin, giving it the second shortest coastline of any county. Meath County Council is the local authority for the county.

Meath is the 14th-largest of Ireland's 32 traditional counties by land area, and the 8th-most populous, with a total population of 220,826 according to the 2022 census. The county town and largest settlement in Meath is Navan, located in the centre of the county along the River Boyne. Other towns in the county include Trim, Kells, Laytown, Ashbourne, Dunboyne, Slane and Bettystown.

Colloquially known as "The Royal County", the historic Kingdom of Meath was the seat of the High King of Ireland and, for a time, was also the island's fifth province. Ruled for centuries by the Southern Uí Néill dynasty, in the late 1100s the kingdom was invaded by the Anglo-Norman conqueror Hugh de Lacy, who ousted the Uí Néill and established himself as the Lord of Meath. This lordship gradually diminished in size before being formally shired as County Meath in 1297, which was further sub-divided into Meath and Westmeath in 1542. The county took its present boundaries in 1977, when much of Drogheda was transferred to County Louth.

Meath has an abundance of historical sites, including the Hill of Tara, Hill of Slane, Newgrange, Knowth, Dowth, Loughcrew, the Abbey of Kells, Trim Castle and Slane Castle. The county was also the site of the seminal Battle of the Boyne, which was fought near Oldbridge in 1690, ending in the defeat of James II and his flight to France. It is the only county in Leinster to have Gaeltacht regions, at Ráth Chairn and Baile Ghib, and is also one of only two counties outside of the west of Ireland to have an official Gaeltacht (the other being County Waterford).

Meath is the 14th-largest of Ireland's 32 counties by area, and the eighth-largest in terms of population. It is the second-largest of Leinster's 12 counties in size, and the third-largest in terms of population. Meath borders seven counties – Dublin and Louth to the east, Westmeath and Offaly to the west, Kildare to the south, and Cavan and Monaghan to the north. Meath's coastline stretches for roughly 20 km (12 mi) along the Irish Sea between the Boyne and Delvin rivers, making it the second shortest coastline of any coastal county. The county town, Navan, is the largest settlement in Meath, and is situated on the River Boyne in the middle of the county. Navan is approximately 50 km (31 mi) from Dublin and 140 km (87 mi) from Belfast.

Owing to the fertile agricultural plains along the Boyne valley, which dominate the county, Meath's landscape is largely rural in nature. However, it is also one of the most densely populated counties in Ireland, with a population density of 94 people per km2. Centuries of exhaustive harvesting and reclamation for agriculture have severely reduced the extent of bogland in the county, especially in comparison to the neighbouring Midland counties. However, small areas of bogland survived, such as Jamestown Bog, Girley Bog and Killyconny Bog, and are currently protected as either Special Areas of Conservation (SACs) or Natural Heritage Areas (NHAs).

The River Boyne, at 112 km (70 mi) in length, is Meath's dominant geographic feature and is synonymous with the county, having defined its history and culture over millennia. The two most prominent tributaries of the Boyne are the Leinster Blackwater, which has its source in Cavan and flows south for 68 km (42 mi) before joining the Boyne at Navan, and the Enfield Blackwater, which has its source in Kildare and flows north for 25 km (16 mi) before joining the Boyne at Donore. In the east of the county, both the River Nanny and the Delvin River flow to the Irish sea, with the latter demarcating the border with County Dublin.

As of 2017, there is a total of 13,326 ha (32,929 acres) of forest cover in the county, representing 5.7% of the total land area. This is an increase from just 11,200 ha (27,676 acres) (4.8%) in 2006. Nevertheless, Meath is Ireland's third-least forested county and remains well below the national average of 11% forest cover. Historically, Meath was extensively forested, but experienced a near total deforestation between the 16th and 18th centuries. Although it has rebounded in recent years, the low forest cover compared to other counties can be explained by the lack of a significant commercial forestry industry within the county. Meath is one of the smallest contributors to the national timber supply, and over two-thirds of Meath's forests are broadleaf – the highest of any county – as opposed to more commercially viable conifers. Additionally, three-quarters of forests within the county are privately owned.