The three letter abbreviation SIP can refer to the following:

• In computing, the IETF standard Session Initiation Protocol.

• In Library Management, Standard Interchange Protocol developed by 3M.

• In the context of Unicode, the Supplementary Ideographic Plane (Plane Two).

• The Scottish Independence Party of Scotland.

• In the context of geoelectric (see Geophysics) Spectral Induced Polarisation.

• In electronics, single in-line package for packaging components.

• Also, see Statistically Improbable Phrases .