southeastern suburb of Dublin, Ireland, and an administrative part of Dun Laoghaire borough, on Dublin Bay. Blackrock grew substantially in the 18th century as a fashionable bathing resort; it developed further with the opening of the Dublin-Kingstown railway in 1834. Blackrock is now a popular seaside resort. Reminders of its former elegance are the 18th-century Maretimo and Frescati houses. Blackrock College, a boys' school, was founded in 1860. Pop. (2006) 28,070.