T-155 Firtina (Storm) is the Turkish variant of the K9 Thunder 155mm self-propelled howitzer of South Korea.

Though essentially using the main systems of the K9 howitzer, including the South Korean designed 155/52 calibre gun system, majority of the chassis, automatic ammunition feeding mechanism, and the German designed MTU-881 KA 500 diesel engine, the T-155 has considerable differences in its turret design, parts of the chassis, the navigation system, and electronic systems (such as the radio and fire control system) which were developed in Turkey. Unlike the K9, T-155 Firtina lacks commander's digital panoramic sight. Through the Inertial Navigation System produced by ASELSAN the howitzer is able to determine the coordinates of the targets at 17.5 meters deviation. Firtina can open fire within 30 seconds.

According to the licence agreement with Samsung Techwin, the first eight T-155s were built in South Korea, while the remaining batch of more than 300 units would be produced in Turkey. The total reported cost of purchase and technology transfer for the Turkish government was $1 billion.

T-155 Firtina has a maximum firing range of 30 to 56 km, depending on the type of ammunition. It can reach a top speed of 66 km/h and has an operational range of 480 km.

The T-155 howitzers are built at the 1st Army Maintenance Center Command of the Turkish Army in Adapazarı. Production rate of the T-155 is 24 units per year. From 2001 to December 2009, more than 150 units have been delivered to the Turkish Army. A total of 350 T-155 Firtina howitzers are planned to be produced.