The Corris Railway (Welsh: Rheilffordd Corris) is a narrow gauge preserved railway based in Corris on the border between Merionethshire (now Gwynedd) and Montgomeryshire (now Powys) in Mid-Wales.

The line opened in 1859, and originally ran from Machynlleth north to Corris and on to Aberllefenni. Branches served the slate quarries at Corris Uchaf, Aberllefenni, the isolated quarries around Ratgoed and quarries along the length of the Dulas Valley.

The railway closed in 1948, but a preservation society was formed in 1966, initially opening a museum; a short section of line between Corris and Maespoeth was re-opened to passengers in 2002. The railway now operates as a tourist attraction. A new steam locomotive was built for the railway, which was delivered in 2005. The two surviving locomotives, plus some of the original rolling stock, are preserved on the nearby Talyllyn Railway.

The gauge of the railway is 2 ft 3 in (686 mm).

In December 1966 a group of dedicated enthusiasts led by Alan Meaden, formed the Corris Railway Society with the aim of preserving what was left of the railway, opening a dedicated museum, and to explore the possibility of reviving some or all of the line. Many of the founding members of the Society were volunteers on the nearby Talyllyn Railway.

Other than at Aberllefenni and Braichgoch quarries, no rails remained in situ along the Corris route. Initially the Society sought to purchase Machynlleth station for its museum, but when this proved impossible it turned its sights elsewhere. The main buildings of Corris station were demolished in 1968 leaving only the adjacent railway stable block standing, and these buildings - badly in need of maintenance - were acquired, along with a short section of trackbed leading southwards. In 1970 the first part of the building was opened as the Corris Railway Museum. A short length of "demonstration" track was laid in 1971.

During the 1970s the Society undertook lengthy negotiations with the relevant authorities to establish the requirements for re-opening the line for passengers, while steadily building up funds and equipment. A new Corris Railway Company, reviving the original name, was incorporated to act as the Society's trading and operating arm, while the Society achieved charitable status. The Museum was extended as more of the building was returned to satisfactory condition.

In 1981 the line's original locomotive shed at Maespoeth was acquired and became the railway's operational base. During the 1980s light track was laid between Maespoeth and Corris, a distance of just under a mile (1.6 km). The formal "first train" back to Corris ran in 1985. In the following years the track was upgraded to passenger standards while negotiations with the authorities continued.

The revived Corris Railway has maintained friendly links with the Talyllyn Railway, which resulted in both of the original Corris locos and rolling stock returning to the railway. In 1996 ex-Corris loco No.4 returned to celebrate its 75th anniversary. In 2003 ex-Corris loco No.3 returned on the occasion of its 125th anniversary with a heritage train of coach No 17, brake van No 6 and two trucks. Corris No.5 has travelled in the opposite direction and has been - so far - the only visiting locomotive to operate passenger trains on the Talyllyn.

In the summer of 2002 passenger services resumed after a break of seventy-two years, initially diesel-hauled. The society has also built a new steam locomotive, to a design based on the Kerr Stuart No.4. This loco arrived on the railway on May 17th 2005 and runs as No.7 (the Corris Railway never officially named its locomotives). No.7 went into service on 20th August 2005, fifty-seven years to the day since the last train on the original railway, and now hauls the regular passenger service between Corris and Maespoeth.

The railway is also actively pursuing a southwards extension towards Machynlleth, with the initial aim of extending the line to Tan-y-Coed, midway between Esgairgeiliog and Llwyngwern and some two and a half miles south of Corris. As always, this is involving lengthy negotiations with the authorities, not least due to the line south of Maespoeth running immediately adjacent to the A487 trunk road. While these are continuing the railway has consolidated its facilities at Maespoeth with the construction of a new two-road carriage shed in the adjacent field (the original carriage sheds at Corris and Machynlleth having been demolished).

Plans to mark the 150th anniversary of the first train on the Corris in 2009, including further locomotive exchanges with the Talyllyn, are currently being formulated.