Day Out With Thomas is a trade name, licensed by Mattel ( HiT Entertainment formerly) for tourist events that take place on heritage railways and feature one or more engines decorated to look like characters from the classic children's Television Show, Thomas the Tank Engine and Friends.
The Nene Valley Railway at Peterborough in England was the very first railway in the world to possess a full-scale replica of Thomas. This was an industrial tank engine built by Hudswell Clarke in 1947. It has been nicknamed "Thomas" due to its bright blue livery and resemblance to the famous tank engine. In 1971, the Rev. W. Awdry made the name official. Later HiT Entertainment tried unsuccessfully to sue the Nene Valley Railway claiming that this loco was breaching their trademark. However, as the name was given by the Rev. Awdry, it has been allowed to remain. However, this "Thomas" does not come under or cannot be used for any "Day Out With Thomas" event[ citation needed].
Since then other tank engines around the world have been dressed up as Thomas. Some heritage railways, most notably the Strasburg Rail Road and Mid Hants Railway, built working locomotives from original engines producing operational replicas of the characters. This caused some controversy among railway preservationists who claimed it disfigured historic locomotives and trivialized the preservation movement. However, those in favor claimed the new projects would draw much-needed visitors and would help associate interest into steam and diesel engines and historical train travel with young children. Since then, railways experienced an increase of income with appearance fees for "Thomases" to railways that do not have a Thomas replica of their own.
From 2008 onwards, many heritage railways in the UK have withdrawn their "Day Out With Thomas" events due to HiT's revised licensing conditions, which includes the requirement for enhanced criminal records (CRB) checks on all the railway's staff and volunteers.  However, the "Day Out With Thomas" events have thrived in the United States and Canada. 
In Australia, several railways have hosted Day Out With Thomas events: in New South Wales the Zig Zag Railway, Lithgow, and the NSW Rail Transport Museum, Thirlmere; in Queensland, the Workshop Rail Museum; and in Victoria the Puffing Billy Railway and the Bellarine Railway.
In New Zealand, Mainline Steam's Bagnall tank locomotive has appeared as Thomas on a number of different locations, including at the Britomart Transport Centre in Auckland and has also appeared at the extremely popular biannual "Day out with Thomas the Tank Engine" weekends at the Glenbrook Vintage Railway, south of Auckland.
Many heritage railways have hosted Day Out With Thomas events; some feature just Thomas himself, and others, such as the Watercress Line, Llangollen Railway, East Anglian Railway Museum, Kirklees Light Railway, Bo'ness and Kinneil Railway and the Caledonian Railway (Brechin) all host Day Out With Thomas events. Currently, 13 Heritage Railways in the UK overall all host Day out with Thomas events. As a result of the licensing costs and other demands made by HiT/Mattel, some railways have replaced their Thomas events with similar ones which also feature engines with faces. For example, the East Lancashire Railway has created "Jimmy the Jinty". 
Nene Valley Railway (unlicensed)
In the United States there are seven traveling Thomas engines: one that is a "real" steam locomotive being Brooklyn Eastern District Terminal number 15, and the other six are dummy engines. All were built or rebuilt by the Strasburg Rail Road.  The dummy engines usually consist of a steam or diesel locomotive operated as a pusher, with an unpowered Thomas engine at the opposite end. Thomas's whistle is powered by the train's compressed air system.  Two are narrow gauge which one has a permanent home operating at Edaville Railroad, while the other five are standard gauge. While in transit between events, Thomas' face is covered. Both standard gauge and the one narrow gauge replicas are transported from location to location via flatbed truck. Thomas appears in full dress at Day Out With Thomas events hosted by railroads in arrangement with HiT Entertainment. Many of the larger railroad museums and tourist railroads across the United States host Day out with Thomas events periodically.  The same trains are also used for the three Canadian events (in BC, Alberta and Ontario). The National Railroad Museum in Green Bay, Wisconsin was the first railroad museum in the United States to host a "Day Out With Thomas" event, unveiling a small Thomas replica in December 1996.
In 2014, all of the Thomas locomotives had their old faces replaced with an animatronic CGI style face. In September 2014, a full-scale replica Percy has also been built. This Percy is also a dummy engine.
Japan's Oigawa Railway started running Thomas events in 2014. the JNR Class C11 (No. 227) was decorated as Thomas. Alongide a JNR Class 9600 (No. 49616) was decorated as Hiro and was displayed at the station yard of Senzu Station and a diesel locomotive that was decorated as Rusty.
In 2015, the JNR Class C56 (No. 44) was decorated as James and operated its own trains alongside Thomas. Also for 2015, a JNR Steam Locomotive that no longer operated on the railway was turned into a Percy replica and sits alongside the Class 9600 that is decorated as Hiro.
In 2016, a red bus, decorated into Bertie, was introduced alongside the Troublesome Trucks, which are pulled by the Rusty replica.
In 2018, a replica of Winston was introduced and guests can ride and operate him by pedalling.
- R. Jones: Major lines pull out of Thomas. Heritage Railway magazine, Issue 106, Dec. 2007, page 26
- "All Aboard for Day Out With Thomas". TicketWeb. Retrieved 10 September 2014.
- Manchester Evening News – "Thomas The Tank Engine Derailed"(accessed 2009-09-08)
- "Day Out With Thomas". Strasburg Rail Road. Strasburg Rail Road Company. Retrieved 10 September 2014.
- Pusher/dummy seen 4 August 2008 at Roaring Camp and Big Trees Narrow Gauge Railroad, operated on standard gauge tracks to Santa Cruz by Santa Cruz Big Trees and Pacific Ry.
- "Day Out With Thomas". TicketWeb. Retrieved 10 September 2014.
Media related to 'Thomas' events on real railways at Wikimedia Commons