The JLC 866 is a watch movement from Jaeger-LeCoultre.

Introduced in 2013, Calibre 866 replaced Jaeger-LeCoultre's Calibre 924, which had been on the market for 8 years. 866 was very similar to 924 but lacks a power reserve indicator.

The 866 is an automatic movement made up of 305 pieces. It runs at 28800 vph, has 32 jewels, and a power reserve of 43 hours. It is a traditional-looking movement with central sweep hands for hour, minute, and date pointer, and a subdial for seconds and moon phase. It also has windows for day and month at 10 00 and 2 00, respectively.

Jaeger-LeCoultre currently uses this calibre in the Jaeger-LeCoultre Master Calendar.