Humberside (/ˈhʌmbərsaɪd/) was a non-metropolitan and ceremonial county in Northern England from 1 April 1974 until 1 April 1996. It was composed of land from either side of the Humber, created from portions of the East Riding of Yorkshire, West Riding of Yorkshire, and the northern part of Lindsey, Lincolnshire. The county council's headquarters was County Hall at Beverley, inherited from East Riding County Council. Its largest settlement and only city was Kingston upon Hull. Other notable towns included Goole, Beverley, Scunthorpe, Grimsby, Cleethorpes and Bridlington. The county stretched from Wold Newton at its northern tip to a different Wold Newton at its southernmost point.

Humberside bordered North Yorkshire to the north and west, South Yorkshire and Nottinghamshire to the south-west, and Lincolnshire to the south. It faced east towards the North Sea.

On 1 April 1996, Humberside was abolished, and replaced with four unitary authority areas: North Lincolnshire, North East Lincolnshire, Kingston upon Hull, and East Riding of Yorkshire. The name has continued in use as a geographical term, mainly in the media, and in the names of institutions such as Humberside Police and Humberside Fire and Rescue Service. These institutions did not change their names mainly due to costs. There were proposals to merge the police force with other Yorkshire forces and then change all the forces' names accordingly. However, these proposals were later ruled out.

Humber Enterprise Zone was launched in 2012 to encourage industrial development at 16 sites around the estuary.

The name "Humberside" was very rarely used, as an informal name and a geographical term, for the area surrounding the Humber before the creation of the ceremonial county. However, by the mid-20th century the industrial development of both sides of the Humber Estuary was becoming increasingly integrated, and "Humberside" was being widely applied to the ports of Hull, Grimsby and Goole and their hinterland. The use of the term to unify the two sides of the river was also driven by the desire of the local authorities in the area to promote the construction of a suspension bridge.

Unlike "Merseyside", which was used colloquially, "Humberside" was adopted as an official term in 1964, when the planning region of Yorkshire and The Humber was created. It consisted of the majority of the former East Riding of Yorkshire and some eastern parts of the former West Riding of Yorkshire and Parts of Lindsey from Lincolnshire. From that time onwards "Humberside" was actively used to market the area. In 1971 the newly launched local BBC radio station was named Radio Humberside, but since the abolition of the county the broadcasters have referred to people of East Yorkshire and North Lincolnshire.

The county was created under the Local Government Act 1972 on 1 April 1974. It covered the former county boroughs of Grimsby and Kingston upon Hull. From Lindsey it incorporated the boroughs of Cleethorpes and Scunthorpe, the urban districts of Barton-upon-Humber and Brigg, and the rural districts of Glanford Brigg, Grimsby and the Isle of Axholme. From the East Riding it took the boroughs of Beverley, Bridlington and Hedon, the urban districts of Driffield, Haltemprice, Hornsea and Withernsea, and the rural districts of Beverley, Bridlington (part), Driffield, Holderness, Howden and Pocklington. From the West Riding it took both the borough of Goole and the rural district of Goole.

The Redcliffe-Maud Report that preceded the Local Government Act 1972 had not proposed any directly analogous area. Instead it proposed making the part north of the Humber one unitary authority, and the part south of it another. The White Paper that followed the Report did not include a cross-Humber authority either, having named the northern part "East Yorkshire" and kept the southern area in Lincolnshire. Humberside had emerged in the Local Government Bill as introduced to Parliament, which also gave it its name for the first time.