Lampacau or Lampacao, also known by other names, was a small island in the Pearl River Delta, which in the mid-16th century played an important role in Sino-Portuguese trade.

The exact location of Lampacau has been a somewhat of a puzzle to the students of the region's historical geography, since both the coastlines and the place names in the area have changed significantly since the 16th century.

The Portuguese maps of the period showed it located somewhat west of Macau, but closer to that city than Shangchuan (São João, "St John's Island") farther to the southwest.

According to the research of Chang Tseng-hsin, making use of both Chinese and Western sources, Lampacau has become connected with the neighboring island of Lianwan (連灣山).

The most recent survey of the literature on that topic is probably the page-long note in Witek & al.[2] It lists the following spelling variants as attested in European sources, mostly Portuguese: Lampacau, Lampacam, Lam Puk, Lanpacan, Lampachan, Lampchào, Lamapacào, Lamapzan, Lanpetan, Lampaço; Lan-pai-kao (in Mandarin) and Long-pa-kao (in Cantonese); Langpetsao.