• Lacuna (manuscripts), a missing section of text
• Lacuna (music), an extended silence in a piece of music
• Lacuna (linguistics), a lexical gap in a language
• Lacuna (law) is the lack of law or of a legal source addressing a situation
• Lacuna (histology), a small space containing an osteocyte in bone or chondrocyte in cartilage
• Lacuna model, a tool for unlocking culture differences or missing "gaps" in text
• Lacunar amnesia, in psychology, amnesia about a specific event
• Lacuna (geology), a large gap in the stratigraphic record, sometimes called a hiatus or unconformity
• Petrovsky lacuna, a region where the fundamental solution of a differential equation vanishes.

Lacuna may also refer to:

• Lacuna Coil, an Italian hard rock/metal band
• Lacuna, Inc., a fictional company in the film Eternal Sunshine of the Spotless Mind
• a character in the Xanth series of books by Piers Anthony
• Lacuna Part I, an indie role-playing game by Jared Sorensen.
• Lacuna (comics) a fictional Marvel Comics superhero and associate of X-Statix.