Day 1 of the 2026 F1 pre-season testing in Bahrain saw all 11 teams on track, with Mercedes, Red Bull, Ferrari, and McLaren competing for dominance. Max Verstappen set the fastest lap with a 1m35.433s on medium tires, leading the field. Oscar Piastri of McLaren posted a notable 1m35.711s on medium tires, while Liam Lindblad topped the timing sheets with a 1m37.964s on soft tires. Mercedes' new power unit drew attention due to its controversial interpretation of engine rules, but the team showed strong performance early on. Williams' boss James Vowles defended Mercedes' engine legality amid rival complaints. Notable car developments include Audi's radically redesigned sidepods, which are narrower and feature vertical inlets to improve airflow, and Red Bull's continued strong performance. The day was marked by several incidents, including Alpine's Franco Colapinto stopping on track and a spin by Lewis Hamilton in his Ferrari. The testing session also highlighted the competitive landscape, with teams like Aston Martin and Haas making progress. Overall, the first day provided insights into team strategies, car performance, and potential season contenders, with ongoing updates expected throughout the Bahrain tests.