The two-door has been unavailable for the past year due to delays in the model undergoing the new WLTP efficiency tests, while the Sportback is making its market debut following a launch in March 2018.
Just 250 of each bodystyle will be sold, exclusively in Audi Sport Edition trim, which is priced from £68,985.
An Audi spokesperson said these 500 units are likely to be the final RS5 models sold before a particulate filter is installed as part of a range update in 2020.
For now, the RS5’s twin-turbocharged 2.9-litre V6 petrol engine produces an unchanged 444bhp and 443lb ft, with drive sent to both axles via an eight-speed automatic gearbox.
Both models are said to dispatch the 0-62mph sprint in 3.9sec. Top speed is unconfirmed but likely to remain an electronically limited 174mph.
The Coupé manages 30.1mpg on the WLTP combined cycle and the Sportback 29.7mpg, with corresponding CO2 outputs of 213g/km and 215g/km.
In Audi Sport Edition form, the RS5 features Anthracite 20in alloy wheels, tinted rear windows, gloss black exterior trim and a performance exhaust system.
Inside, the seats are finished in Alcantara and leather, with LED ambient lighting, Apple CarPlay, Android Auto, blindspot monitoring and a panoramic sunroof fitted as standard.
The return of the RS5 comes as Audi begins to bring its entire range back to market following a 3.5% drop in profits last year as newly implemented WLTP regulations forced the withdrawal of each for testing.