Carrickmacross (Irish: Carraig Mhachaire Rois, meaning 'rock of the wooded plain') is a town in County Monaghan, Ireland. The population was 5,745 at the 2022 census, making it the second-largest town in the county. Carrickmacross is a market town which developed around a castle built by the Earl of Essex in 1630. The town is 20km west of Dundalk and 75km north-north-west of Dublin city centre and 106km south west of Belfast. Carrickmacross won the European Entente Florale Silver Medal Award in 1998.

Carrickmacross is a market town which developed around a castle built by the Earl of Essex in 1630. The Convent of St Louis now stands on the original castle site, as the castle itself was destroyed in the late 17th century during the Williamite Wars.

The town developed further as a market town during the 18th century, and a number of large municipal and religious buildings were built to serve the growing population during the 19th century. The town experienced population decline in mid- to late-19th century, during the Great Famine, with the population decreasing from 2,063 in 1861 to 1,779 inhabitants by 1891. The town's Poor Law Union Workhouse and Fever Hospital were built in this period - the latter later becoming the offices of the Urban District Council which was originally formed in 1899.

Among the historic buildings in the town is the Roman Catholic church which was completed in 1866 and is dedicated to Saint Joseph. It contains ten stained-glass windows which were designed by the artist Harry Clarke in 1925. The town's Church of Ireland church, dedicated to Saint Finbarr, is older, and was built c.1770 before being remodelled c.1845.

Magheross Church, located on the outskirts of the town, is also of historical interest, and originally dates from c.1550. Other notable buildings include the Carrickmacross Courthouse (built in 1837) and the restored Poor Law Union Workhouse (built in 1841).

The grave of Patrick Byrne (1794–1863), the last major exponent of the Gaelic harp and the first Irish traditional musician ever photographed, is in the area.^{[citation needed]}

The town is known for the lace bearing its name. Carrickmacross lace is worked in an individual style, devised by Mrs Grey Porter, wife of the rector of Donaghmoyne, who introduced it in 1820. When she left the district the teaching of Carrickmacross lacemaking was continued by Miss Reid of Rahans, but it was only after the Great Famine in 1846, when a lace school was set up by the managers of the Bath and Shirley estates at Carrickmacross as a means of helping their starving tenants, that the lace became known and found sales.

Subsequently, the lacemaking declined, but in the last decade of the 19th century the Sisters of St Louis founded their own lace school to revive the craft, and this was quite profitable for several years. Although the outbreak of the 1914–18 war marked the virtual end of commercial production of hand-made lace in Europe, the lace school kept the technique alive throughout most of the 20th century. In 1984 the St Louis Sisters assisted in the formation of the Carrickmacross Lace Co-operative, which maintains the tradition to this day.