Blue box is an early phreaking tool that simulates a telephone operator's dialing console.

Blue box may also refer to:

• Link Trainer or Blue Box, a flight simulator
• Blue Box, a Mac OS 8 emulation layer from the Rhapsody OS which became the Mac OS X Classic Environment
• MXR Blue Box, an octave effect for electric guitars
• Nickname of Hessdalen AMS, as it uses a blue container

• TARDIS, or "the blue box", a time machine and spacecraft in the British TV series Doctor Who
• Blue Box (novel), a Doctor Who novel by Kate Orman
• Blue Box (album), a 1996 album by Kate Ceberano
• Blue Box (manga), a manga series by Kouji Miura
• Bluebox Limited, a film production company

• Blue Box, common name for the tree species Eucalyptus baueriana and Eucalyptus magnificata
• Blue box (WTO agreement), a subsidy category of the World Trade Organization
• Blue box recycling system, initially a waste management system used by Canadian municipalities
• A nickname for Kraft Dinner packaged stovetop macaroni and cheese
• A British police box
• A severe thunderstorm watch, in meteorology
• JNF collection boxes, Jewish National Fund blue charity collection boxes