There is evidence of a Roman camp near St Elli shopping centre but it is unknown when it was built, and it was completely abandoned shortly after construction either due to the Romans thinking the area was completely worthless or due to a raid by either rebellious local Britons or an Irish raid.

During the post-Roman period, the area of Llanelli may have been heavily populated with Pagans as there's evidence of a pagan worship temple under the Saint Elli church, it may have had frequent raids from Brycheiniog and Dyfed in order to Christianise the area to which it would eventually fall into Dyfed.

During the early medieval period, it is said a saint named Elli, or Ellyw,[4] who in legend is the son or daughter of King Brychan established a church on the banks of the Afon Lliedi.

[8] The current St Elli's Church dates from the 14th century although extensive restorations were completed in 1911.

[13] There are several theories on this nickname: Llanelli allowed the docking of a Turkish ship when Swansea dockers were on strike in the 1920s, Llanelli tinplate workers wrapped their heads like turbans to deal with sweat, or it is a reference to the 4th Battalion of the Welch Regiment fighting against the Ottoman Empire in the Middle Eastern theatre of World War I.

[17] In the mid-20th century, Llanelli was the world's largest town in which more than half the inhabitants spoke a Celtic language.

According to the 2011 UK Census returns, 23.7 per cent of Llanelli town residents habitually spoke Welsh.

However, the area around Llanelli is a Welsh stronghold, in which 56 per cent do so in communities such as Llwynhendy and Burry Port.

The council reacted by sending in the bailiffs and selling their furniture to recover the money owed.

The council finally reversed its policy in the 1960s, giving Welsh equal status with English.

[19] In 1991 Llanelli was a distinct travel to work area, but a 2001-based revision has merged it into a wider one of Swansea Bay.

James Buckley was an ordained Methodist minister, born in Oldham, Lancashire in 1770, who after moving to Llanelli towards the end of the 18th century became involved in establishing a small brewery.

In the past decade, the longstanding emphasis on heavy industry has shifted towards the tertiary sector employment in leisure and tourism.

Ongoing developments include the new Llanelli Scarlets rugby stadium, the Old Castle Works leisure village (see below) and a National Hunt racecourse at Ffos Las near Trimsaran.

[26] Machynys Ponds, a Site of Special Scientific Interest notable for its dragonfly population, lies a mile to the south.

Llanelli has an Islamic centre on Station Road[41] and Baptist churches spread throughout the town and surrounding areas.

Previously they had played at Stradey Park, home to Llanelli RFC for over 130 years and one venue used for the 1999 Rugby World Cup, hosting the match between Argentina and Samoa on 10 October 1999.

On 31 October 1972, in one of the most famous results in rugby union history, Llanelli beat the New Zealand national team 9–3 in front of around 20,000 spectators.

Llanelli centre Roy Bergiers scored the only try of the game, charging down a clearance by All Black scrum-half Lin Colling after a penalty from Phil Bennett rebounded back into play off the crossbar.

There is a strong junior rugby core, including club sides such as Felinfoel, New Dock Stars, Llangennech and the Llanelli Wanderers.

In 2005, Coedcae School won the Inter-Schools Cup of Wales with an 8–5 victory over Brynteg Comprehensive.

Stebonheath Park is the home of football club Llanelli A.F.C., which plays in the Cymru South.

The town has many active local teams and tournaments such as the 2018 Challenge Cup, where West End United beat Trostre Sports AFC.

Llanelli is the birthplace and home of Terry Griffiths OBE (1947–2024), snooker world champion in 1979 and runner-up in 1988.

Services from Llanelli railway station on the Great Western Crescent south of the town centre connect with Fishguard Harbour and Swansea along the West Wales Line.

The district is also served by stations at Bynea, Llangennech, Pembrey & Burry Port and Kidwelly.

[62] The town forms part of the Llanelli parliamentary constituency, currently represented by Nia Griffith MP of the Labour Party.

[74] Llanelli Waterside, a joint venture between Carmarthenshire County Council and the Welsh Assembly Government, aims to transform the waterfront into a business, leisure and residential community.

Pentre Nicklaus Village, located on the Machynys Peninsula has been criticised for being above the price range for local people.