Castlebar ("Barry's Castle") is the county town of County Mayo, Ireland.

A campus of Galway-Mayo Institute of Technology and the Country Life section of the National Museum of Ireland are two important local amenities. The town is linked by railway to Dublin, Westport and Ballina.

Castlebar is the location for important festivals and traditions, among which is the International Four Days' Walk. A well-established blues music festival in venues across the town took place for many years on the weekend before the first Monday in June, but has not taken place since 2011. During the 1970s and 1980s the town hosted the International Castlebar Song Contest which was televised nationally on RTE. The Museum of Country Life is located on the outskirts of Castlebar, and is the only branch of the National Museum of Ireland located outside Dublin.

Castlebar is home to The Linenhall Arts Centre, which exhibits visual art throughout the year, as well as hosting live drama and music performances.[13] The Linenhall also organises an annual children's arts festival called Roola Boola (an anglicisation of the Irish phrase rí rá agus ruaile buaile which in this context means "boisterous fun"). The Royal Theatre and Event Centre, with a capacity of two thousand two hundred fully seated, four thousand standing, hosts larger-scale productions and popular music concerts.

There are Roman Catholic, Church of Ireland (Anglican), Elim Pentecostal, and evangelical (Calvary Church Castlebar) churches in the town. There are also several Spiritualist gatherings. There is a recently established Mayo male voice choir and Mayo Concert Orchestra. There is also a marching band in the town - one of the few surviving marching bands west of the Shannon. Throughout the 1980s and 1990s, Castlebar experienced significant immigration, growth and investment.