Neighbouring communities are Whitchurch to the east on the opposite bank of the River Taff, Pentyrch to the west with St Fagans and Llandaff to the south.

Evidence of Stone Age occupation of the Lesser Garth Cave near Morganstown was discovered in 1912 and included worked flints.

[3] Hints about the derivation of the name Radyr can be found in Lifris's writings Life of St Cadog, written between 1081 and 1104 but relating to the earlier period around AD 530, which mentions a croft or tref on the site called Aradur Hen.

[3] On his death Sir George's lands passed to his eldest son William, who also became an MP and invested in the Pentyrch ironworks.

It comprises about eleven hundred acres of arable and pasture land, inclosed and in a profitable state of cultivation: the surface is in some parts elevated, and in others flat, but nowhere subject to inundation; the soil is a strong brown earth, favourable to the production of good crops of grain of all kinds, potatoes, and hay.

Radyr Court, formerly the seat of the family of Matthew, ancestors of the late Lord Llandaf, has been partially taken down, and the remainder has been modernised, and converted into a farmhouse.

The turnpike-road leading from Cardiff to Llantrissent passes a little to the south of the parish; and the Tâf-Vale railway runs through it, nearly parallel with the river, which is crossed by the line in this vicinity.

Some of the inhabitants are employed at the iron-works in the parish of Pentyrch.The living is a vicarage, endowed with £200 royal bounty; patron and impropriator, the representative of the late Earl of Plymouth, who is lord of the manor: the tithes have been commuted for £113.

In the parish is a spring of very cold water, called Y Pistyll Goleu, "the bright water-spout," issuing from the side of a hill, under a considerable depth of earth over a limestone rock: it has by some writers been termed mineral, but it is not known to possess any other properties than that of its extreme coldness, which renders it efficacious in curing sprains and weakness of the sinews."

In the First World War the community raised funds for a "Radyr bed" at the nearby Welsh Metropolitan Military Hospital in Whitchurch and established a "Citizen Guard" made up of those too old or too young to enlist.

One evacuee from Woolwich, Patricia Armstrong aged nine, was knocked down by a passenger train and killed on a Saturday afternoon in May 1943 while using the Gelynis foot crossing at Morganstown.

[18] As air raids on Cardiff increased, even younger children from Radyr were evacuated to boarding schools at Rhoose and Bridgend.

[20] Danybryn Woods, near the development, was retained as the entire forest is protected by a tree preservation order and is home to many species of plants and wildlife.

[20] In 2017 construction started on the first phase of a new Cardiff suburb of 7,000 houses, named Plasdwr, on countryside along the Llantrisant Road between Radyr and St Fagans.

[30] From 1749, iron from Pentyrch was initially transported to the works using pack-horses, then tub boats were used on the Taff passing onto the feeder via a lock at Radyr Weir.

The Radyr Weir scheme channels more than 500 million cubic metres of water per year through two screw turbines and is expected to generate 400 kW — enough energy to power three of the city’s leisure centres — which will save 700 tonnes of CO2 annually.

[34][35] The Community Woodlands have a network of footpaths and boardwalks and includes evidence of Iron Age settlements and remains of an early cooking hearth.

[37] Radyr hawkweed is the common name of Hieracium radyrense, a very rare endemic member of the aster, daisy, or sunflower family.

[38] In the first survey of 1998, only nine plants were identified in one single Radyr garden, where it traditionally grew on grassy banks and lawns, often in shade.

Neither the species nor the sites have any current legal protection, and it could be under significant threat of survival in the long term from inappropriate gardening or care.

[38] The plant normally flowers between May and early July and Radyr residents are urged by botanists to be on the look out for further examples of the endangered species while walking in the area.The 2001 census showed that the suburb had a total population of 4,658, of whom 2,268 were male and 2,390 were female.

Designed by the Llandaff diocesan surveyor George Halliday, the nave was ready for use at Easter 1904 and the chancel and tower were completed in November 1910.

Again with the help of Plymouth Estates, the club lifted the turf from all three grass courts and relaid it on its current site next to Christ Church on Heol Isaf.

[57] Radyr Cricket Club was founded in 1890 by the Earl of Plymouth, who granted a hundred-year lease for the current riverside ground to the local residents for a nominal sum.

Radyr railway station still handles significant traffic, with over 200 trains calling each weekday and more than 400,000 passenger journeys per year.

[64] The northern "Lisvane and Radyr route" for the M4 was eventually chosen after a number of noisy public enquiries and active objections by residents from both communities.

[13][67] He called it an "imposing country mansion, surrounded by acres of farm and woodland" in his book Boy: Tales of Childhood.

Local sportsmen include Harry Corner (1874–1938), an English cricketer who played in the Great Britain team that won a gold medal at the 1900 Summer Olympics, who lived, died and was buried in Radyr.

[72] Frank Meggitt (1901–45), a Welsh cricketer, a right-handed batsman and wicket-keeper who played for Glamorgan, also lived in the town after retiring from the sport.

The outdoor scenes in an episode of the TV science fiction series Torchwood, called Small Worlds, were filmed mostly around Radyr Primary School.