The Lamborghini Veneno Roadster has been officially unveiled with confirmation that it will be less exclusive but even more expensive than the extreme coupe on which it's based.

Lamborghini will build nine Veneno Roadsters - three times more than the number of coupes - and will sell them for 3.3 million euro, a price tag that would translate to roughly $6.5 million if sold in Australia.

The cherry atop the iconic Italian supercar maker's 50th anniversary celebrations, the Lamborghini Veneno Roadster becomes the brand's most powerful and fastest ever open-top model.

Employing the same uprated, Aventador-sourced 552kW 6.5-litre V12, seven-speed sequential transmission and all-wheel-drive system as the coupe that debuted in Geneva in March, the Veneno Roadster launches from 0-100km/h in 2.9 seconds (0.1sec slower) and on to an identical 355km/h top speed.

Dubbed an 'open racing prototype', the Veneno Roadster comes without a roof, instead featuring a strong rollover bar for "optimum safety".

At 1490kg, the Roadster is 40kg heavier than the Veneno coupe but still 85kg lighter than the Aventador courtesy of widespread use of carbonfibre throughout its monocoque racing chassis, body panels and cabin fittings.

Supporting the lightweight design is the Veneno Roadster's extreme aerodynamics, which Lamborghini says create "perfect airflow and downforce" - the front end working like a large aero wing, the smooth underbody and side openings channelling air to the engine and diffuser, and the adjustable rear wing providing balance between the flowing forces.

The intense 'Rosso Veneno' paint colour has been developed exclusively for the Roadster, though Lambo says each customer will be able to individualise their car to suit their preferences.

True to tradition, the Lamborghini Veneno is named after a fighting bull renowned for its speed.

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