Calibre 2003 is an ultra-thin hand-wound watch movement from Audemars Piguet.

This was the thinnest watch movement made from 1946.

Cal. 2003 was introduced in 1946 or 1953 as the thinnest watch movement available. It achieved this goal by passing the Piguet 21, introduced in 1925, by .1 mm The F. Piguet movement was 1.75 mm and this Cal. 2003 was 1.64 mm. Both measured 9 ligne in diameter, making them extremely small as well. Cal. 2003 was designed in cooperation with LeCoultre and Vacheron Constantin.

The movement was based on the Audemars Piguet 9ML but with many modifications, specifically to the bridges. Audemars Piguet had exclusivity for two years before Vacheron Constantin introduced their own version, their Cal. 1003. Jaeger-LeCoultre never used the calibre themselves, but they did produce it as Cal. 803 for others to use.

The movement is extremely simple, with manual winding, 18,000 A/h beat rate, and 17 or 18 jewels. The thin profile makes it ideal for modules, and this is how it is typically employed.

• Vacheron Constantin 1003
• JLC 803

• Piguet 21, which had the record before