IEC 61508 is the international standard for the functional safety of electrical, electronic and programmable electronic safety related systems.

It sets out the requirements for ensuring that systems are designed, implemented, operated and maintained to provide the required safety integrity level (SIL). Four SILs are defined according to the risks involved in the system application, with SIL4 being applied for the highest risks. The standard specifies a process that can be followed by all links in the supply chain so that information about the system can be communicated using common terminology and system parameters.

Other standards related to the application of the IEC 61508 approach with specific relevance to particular sectors include IEC 61511 relating to process industries, IEC 61513 relating to nuclear industries, and IEC62061 relating to the machinery sector.