The earliest model railways were the 'carpet railways' in the 1840s. Electric trains appeared around the start of the 20th century, but these were crude likenesses. Model trains today are more realistic. Today modellers create model railroad layouts, often recreating real locations and periods throughout history.

Railway modelling (UK, Australia and Ireland) or model railroading (USA and Canada) is a hobby in which rail transport systems are modelled at a reduced scale.The scale models include locomotivesrolling stockstreetcarstrackssignalling, and roads, buildings, vehicles, model figures, lights, and features such as streams, hills, and canyons.

Involvement ranges from possession of a train set to spending hours and large sums of money on a large and exacting model of a railroad and the scenery through which it passes, called a "layout". Hobbyists, called "railway modellers" or "model railroaders", may maintain models large enough to ride (see Live steamRidable miniature railway and Backyard railroad).

Modellers may collect model trains, building a landscape for the trains to pass through. They may also operate their own railroad in miniature. For some modelers, the goal of building a layout is to eventually run it as if it were a real railroad (if the layout is based on the fancy of the builder) or as the real railroad did (if the layout is based on a prototype). If modelers choose to model a prototype, they may reproduce track-by-track reproductions of the real railroad in miniature, often using prototype track diagrams and historic maps.

Layouts vary from a circle or oval of track to realistic reproductions of real places modeled to scale. Probably the largest model landscape in the UK is in the Pendon Museum in OxfordshireUK, where an EM gauge (same 1:76.2 scale as 00 but with more accurate track gauge) model of the Vale of White Horse in the 1930s is under construction. The museum also houses one of the earliest scenic models - the Madder Valley layout built by John Ahern. This was built in the late 1930s to late 1950s and brought in realistic modelling, receiving coverage on both sides of the Atlantic in the magazines Model Railway News and Model RailroaderBekonscot in Buckinghamshire is the oldest model village and includes a model railway, dating from the 1930s. The world's largest model railroad in H0 scale is the Miniatur Wunderland in HamburgGermany. The largest live steam layout, with 25 miles (40 km) of track is 'Train Mountain' in Chiloquin, OregonU.S.

Model railroad clubs exist where enthusiasts meet. Clubs often display models for the public. One specialist branch concentrates on larger scales and gauges, commonly using track gauges from 3.5 to 7.5 inches (89 to 191 mm). Models in these scales are usually hand-built and powered by live steam, or diesel-hydraulic, and the engines are often powerful enough to haul dozens of human passengers.

The Tech Model Railroad Club (TMRC) at MIT in the 1950s pioneered automatic control of track-switching by using telephone relays.

The oldest society is 'The Model Railway Club' (established 1910), near Kings Cross, London, UK. As well as building model railways, it has 5,000 books and periodicals. Similarly, 'The Historical Model Railway Society' at Butterley, near Ripley, Derbyshire specialises in historical matters and has archives available to members and non-members.