The J12 was Chanel's first sports watch, in black ceramic. Chanel's history dates its creation to 2000, while Wikipedia gives 1999. It was designed by Jacques Helleu, the house's longtime artistic director, who drew on his two passions, cars and sailing.
Chanel used highly scratch-resistant ceramic for the case and the bracelet, an unusual choice at the time. The watch was conceived as unisex, sturdy enough for sport but still a fashion object, and Wikipedia notes it helped fashion houses to be taken seriously as watchmakers. Arnaud Chastaingt, head of Chanel's watch studio from 2013, called it "the first revolution of the watch world in the 21st century".
A white ceramic version followed in 2003, which the house says introduced white into watchmaking. In 2019 Chanel took a stake in the Swiss movement maker Kenissi, whose Caliber 12.1 powers the redesigned 38mm self-winding J12. The white J12 with that movement won the ladies' prize at the Grand Prix d'Horlogerie de Genève.