Power comes from a 2.0 TFSI that pushes out 231hp and 370nm of torque.
Audi says the Audi S1 and the S1 Sportback (five-door) set the benchmark in their class for dynamic performance.
0-100 km/h takes 5.8 and 5.9 seconds respectively. Top speed is 250km/h.
S1 consumes 7.0 litres of fuel per 100 kilometres, while producing 162g of CO2 per kilometre.
The suspension on the two compact sport models has been extensively revamped, along with the electromechanical power steering.
Modified pivot bearings on the front axle enhance spontaneity when turning.
At the rear, a four-link design replaces the compound link rear suspension used on the A1 models.
The Audi drive select dynamic handling system comes with a range of settings to vary the response of the engine and the standard variable shock absorbers.
Styling-wise, S1 and S1 Sportback are instantly recognisable as flagship models in the A1 model line.
Their xenon plus headlights are all-new, while the LED rear lights come with new, horizontally structured graphics. A host of details - particularly on the front and rear bumper, the side sills and the exhaust system - boast more striking styling.
Four new exterior colours supplement the available paint finishes.
The optional quattro exterior styling package hones the look further, courtesy of features such as a large roof spoiler.
"The Audi S1 offers all the virtues of a sports car, great performance, direct handling and permanent quattro drive that puts the power to the road in a superior way," said Prof Dr Ulrich Hackenberg, Audi Board Member for Technical Development.
He added: "The quattro drive has a large following of fans, which is sure to become even larger thanks to the offering in this segment."
The Audi S1 starts at €36,970 (Sportback €37,570) on the road.
