T5 can mean:

• Turkmenistan Airlines, IATA airline designator
• Terminal 5 at London Heathrow Airport, due to open in 2008.
• A kind of topological space, see Normal space
• A type of high output fluorescent lamp with an external diameter of 5/8th of an inch
• T5 spinal nerve
• Fifth thoracic vertebra of the vertebral column, in human anatomy
• Taylor T5 Thinline Fiveway (acoustic/electric guitar)
• Telecinco, Spanish TV station
• Thunderbird 5, one of the rescue vehicles in the series Thunderbirds
• The designation of the series V Volkswagen Transporter van
• The high-performance T5 engine used in T5 model Volvo cars.