The Gwili Railway (Welsh: Rheilffordd Gwili) is a Welsh heritage railway, that operates a preserved standard gauge railway line from the site of Abergwili Junction (near Carmarthen) in southwest Wales along a four-and-a-half-mile (7.2 km) section of the former Carmarthen to Aberystwyth line. The original railway closed in 1965, with the track being lifted in 1975.

The broad-gauge railway was opened in 1860 from Carmarthen to Conwil (now Cynwyl)

In 1872, the line became the last in Wales to be converted from Brunel's 7 ft 1⁄4 in (2,140 mm) gauge to 4 ft 8 1⁄2 in (1,435 mm) standard gauge.

Trains on the Gwili start from Bronwydd Arms where the replica GWR station is dominated by a Signal Box saved from Llandybie railway station on the Heart of Wales Line. The Signal box, which is open to the public, was built in 1885 and has been restored to operate signalling within the station area.

Typical features on the line include the gradients such as the 1 in 60 on the bank immediately north of Bronwydd Arms, the meandering River Gwili and the A484 road which are never far away and the wooded forests and sharp curves as the railway twists its way through the valley.

Peckett 0-4-0ST 'Olwen' at Bronwydd Arms

From Bronwydd, the line climbs between rural hills and meadows alongside the river River Gwili past the site of the first terminus of the newly opened Gwili Railway next to the old mill at Cwmdwyfran. From here, the line continues climbing until it passes under a rusticated brick bridge at the second terminus at the now defunct Penybont station.

The line carries over a redecked bridge crossing the River Gwili. This expansion was achieved in time for its 10th anniversary celebrations in 1988. At the same time, the new terminus of Llwyfan Cerrig was opened to the public.

In 2001, a further one-half mile (0.8 km) extension built by volunteer labour was opened to a new halt at Danycoed.

Llwyfan Cerrig (in English, Stone Platform) was a former quarrymen's halt and the Gwili Railway has created a nature trail which winds through the old quarry and emerges above the stock sheds. The station building, which originally stood at Felin Fach on the Aberaeron branch and dates from 1911, was dismantled by volunteers and re-erected in the early 1990s. It has been restored and furnished to an authentic 1950s style.

From the platform, a path leads to a picnic area on the bank of the Gwili River where kingfishers and heron can sometimes be glimpsed. A miniature railway runs from this station and refreshments can be bought.

From Llwyfan Cerrig, the line runs uphill for another one-quarter mile (0.40 km) with the River Gwili on one side and a rock face on the other, until it reaches the present end of the line at Danycoed (English translation being 'under the wood') where a typical GWR rural halt has been recreated.

Operationally, the railway is normally run on a 'one engine in steam' basis although the facility exists to pass trains at Llwyfan Cerrig at busy periods such as Day Out With Thomas events. In recent years, the Railway has expanded the portfolio of events on offer with Dining Trains, Driver Experience days and Jazz and other themed nights now being part of the annual timetable.