The McLaren P1 GTR is the track-only, circuit-focused sibling of the road P1 and the ultimate expression of the Ultimate Series hybrid hypercar. Revealed as a design concept at the 2014 Pebble Beach Concours and put into production in 2015 after the road cars were finished, it was offered only to people who already owned a P1 road car. It shares the P1's carbon "MonoCage" tub, twin-turbo M838TQ V8 and integrated e-motor, but is uprated to about 986 hp (1,000 PS) and shed roughly 110 lb (~50 kg), with fixed track aero and slick tires. It is not road-legal.

The GTR program was tied to the 20th anniversary of the McLaren F1 GTR's 1995 Le Mans overall win, which is also why Lanzante, the team that ran that winning F1 GTR, later converted a handful of P1 GTRs back to road-legal specification as the P1 LM. About 58 GTRs are widely reported, but because it was a bespoke owners-only program its exact final count is not independently audited. It launched at about $3.0 million (converted from its 2015 UK-only price) before local taxes.