Tandem (or in tandem) is an arrangement in which a team of machines, animals or people are lined up one behind another, all facing in the same direction.

Tandem Computers, Inc. was the dominant manufacturer of fault-tolerant computer systems for ATM  networks, banks, stock exchanges, telephone switching centers, and other similar commercial transaction processing applications requiring maximum uptime and zero data loss. The company was founded in 1974 and remained independent until 1997. It is now a server division within Hewlett Packard.