Botallackite, chemical formula Cu2(OH)3Cl is a secondary copper mineral, named for its type locality at the Botallack Mine, St Just in Penwith, Cornwall.

[2] It was first described in 1865 for an occurrence in the Botallack mine, Cornwall, England, and named for the type locality.

[2] Botallackite forms in copper deposits exposed to weathering and salt water.

[2] It is reported from black smoker deposits due to reaction of primary sulfide minerals with seawater.

Minerals associated with botallackite include atacamite, paratacamite, brochantite, connellite and gypsum.