Necklace and Calabash is a gong'an detective novel written by Robert van Gulik and set in Imperial China (roughly speaking the Tang dynasty).

It is a fiction based on the real character of Judge Dee (Ti Jen-chieh or Di Renjie), a magistrate and statesman of the Tang court, who lived roughly 630–700.

Judge Dee is a magistrate in the fictional Poo-yang district, a wealthy area through which the Grand Canal of China runs (part of modern-day Jiangsu province).

The Emperor's daughter lives in the district at the Water Palace, which falls under a special administration run by the military commander.

Judge Dee goes to the area for a few days of relaxing fishing but soon meets with a strange Taoist hermit; next a body is found in the river.