First South Yorkshire

In 1989, South Yorkshire Transport introduced the Mainline brand on certain bus routes around South Yorkshire. Buses operated with Sheffield Mainline names in a bright red and yellow livery, replacing the previous "coffee and cream" livery. It was followed by Doncaster Mainline in a silver grey and red livery relieved by a light yellow band and finally Rotherham Mainline, whose buses were painted blue and yellow. In 1992, the local brands were dropped and Mainline became the standard fleetname across the company's operating area. A common red and yellow livery with silver and blue bands was introduced.

In November 1993, Mainline was sold to its employees in a management buyout. Shortly after, Stagecoach Holdings purchased a 20% stake in the company, however this stake was ordered to be divested by the Office of Fair Trading in 1995. The stake in Mainline would be purchased from Stagecoach by FirstBus for £1.6 million in January 1996.

In 1998, FirstBus purchased the remaining 80% shareholding and renamed the business First Mainline. Buses were repainted in a simplified red and yellow livery, reminiscent of the original 1989 Sheffield Mainline livery. In 2000 First Mainline was rebranded as First South Yorkshire and the corporate light grey, blue and pink livery introduced.

In 2013, First South Yorkshire began to paint buses into First's new Olympia corporate livery, which is an updated version of the former livery. At the same time, the individual First Sheffield, First Rotherham, First Doncaster and First X78 brands were introduced. The First X78 brand was superseded by the Steel Link brand in 2015, while the First Rotherham brand was retired with the closure of the Rotherham depot in 2017.

The operations of First South Yorkshire and First Midlands, consisting of First Potteries, First Leicester and First Worcester, merged on 1 June 2020 to form First South Yorkshire & Midlands. The new company would be managed by First Midlands CEO, Nigel Eggleton. The aim of this merger was to revitalise bus services in both merger regions, following a period of poor customer service by First South Yorkshire.

Services

First South Yorkshire operate services in Doncaster, Rotherham and Sheffield. Due to bus services history and number changes, some routes share service numbers within South Yorkshire.

Route X78 is an express service which runs from Sheffield Interchange to Doncaster Frenchgate Interchange via Meadowhall, Rotherham and Conisbrough. In 2016, 22 Wright StreetDecks, some of which were originally intended for the Steel Link, were placed in service on the X78 as part of an initiative to improve Rotherham's bus services.

In September 2016, Steel Link X1 express route commenced operating from Sheffield to Maltby via the Bus Rapid Transit North scheme. Eighteen Wright StreetDecks with high-specification interiors were purchased for the service.

First South Yorkshire also operate Peak District services 271 and 272, from Sheffield, across the South Yorkshire boundary and into Derbyshire in the Peak District. In 2021, a double-decker bus was branded in green 'Peak Link' livery for these services. In May 2025 First South Yorkshire received a batch of 7 2022 low-height Wright StreetDecks for the service.