The Sony α55 (model variants SLT-A55V with GPS, SLT-A55 without GPS depending on country) is a midrange-level SLT camera, released in August 2010.

Its design is novel due to its being the first digital single-lens translucent camera, along with the Sony α33. As an SLT it employs a semi-transparent mirror instead of an opaque mirror, which enables phase detection auto focus in live view. The design also replaces the optical viewfinder present in conventional DSLR with a high-resolution electronic viewfinder. The translucent mirror is fixed in position so does not have to flip up to take a still image, enabling rapid continuous shots of up to 10 frames per second. The static mirror also eliminates "mirror slap", the noise produced by the movement of the mirror during a shutter actuation, making the A55 quieter than standard DSLRs. The A55 is one of the first four Sony Alpha DSLR / SLT cameras with video mode included, capable of 1080i. It is also capable of shooting 1080p at 30fps. The SLT design means that it is capable of using phase-detection autofocus during video recording. It has body-integrated image stabilization, and a 16.2 MPx APS-C CMOS sensor.

Sony Alpha, stylized as Sony α (Greek letter alpha), is a digital SLR camera system introduced on 5 June 2006. It utilizes and expands upon Konica Minolta camera technologies, including the Minolta AF SLR lens mount, whose assets were acquired by Sony after the end of Minolta's camera operations in early 2006. Sony also has an 11.08% ownership stake in Japanese lens manufacturer Tamron, which is known to have partnered with Konica Minolta and Sony in the design and manufacture of many zoom lenses.

Prior to the acquisition by Sony, the α branding had already been used on the Japanese market by Minolta for their AF camera system (marketed as "Dynax" in Europe, and "Maxxum" in North America.) Sony adopted the name "A-mount system" for the Minolta AF lens mount which has been retained in their new SLR range.

Sony's entry into the DSLR market dates back to July 2005 where a joint venture with Konica Minolta would have resulted in both companies marketing an updated line of DSLRs to the masses. Between 2006 and 2008 Sony was the fastest growing company on the DSLR market, reaching 13% market share in 2008 to become the third largest DSLR company in the world. In August 2011, Sony confirmed that it is working on the production of full-frame Alpha cameras. In May 2010, Sony introduced two Alpha NEX mirrorless interchangeable lens cameras equipped with proprietary Sony E-mount.