In communications, a system is wideband when the message bandwidth significantly exceeds the coherence bandwidth of the channel. Some communication links have such a high data rate that they are forced to use a wide bandwidth; other links may have relatively low data rates, but deliberately use a wider bandwidth than "necessary" for that data rate in order to gain other advantages; see spread spectrum.

A wideband antenna is one with approximately or exactly the same operating characteristics over a very wide Passband. It is distinguished from broadband antennas, where the passband is large, but the antenna gain and/or radiation pattern need not stay the same over the passband.

The term Wideband Audio or (also termed HD Voice or Wideband Voice) denotes a telephony using a wideband codec, which uses a greater frequency range of the audio spectrum than conventional voiceband telephone calls, resulting in a clearer sound. Wideband in this context is usually considered to cover frequencies in the range of 50–7,000 Hz, therefore allowing audio with richer tones and better quality.^{[citation needed]}

According to the United States Patent and Trademark Office, WIDEBAND is a registered trademark of WideBand Corporation, a US-based manufacturer of Gigabit Ethernet equipment.^[1][2]

Within Australia and New Zealand, the word WIDEBAND is a registered trademark of "Wideband Technology Pty Ltd", an Australian-based company specialising in data and communication equipment.^[3]

In some contexts wideband is distinguished from broadband in being broader.^[4]