DIALux is a three-dimensional (3D) modeling and graphic design software developed and sold by DIAL GmbH (Lüdenscheid, Germany) for lighting planning. It is mainly used by lighting planners, consultants, architects, lighting technicians and electricians to plan, calculate and visualize light in indoor and outdoor areas. Many lamp and luminaire manufacturers offer "Add-on (IT)" add-ons for their products that make the light intensity distribution characteristics available in Dialux.

Dialux supports, among other things, the lighting planning of sports facilities or the planning of emergency lighting in accordance with various standards such as the German and European standard DIN EN 1838. In addition, it offers functions for daylight simulation and intrusive light calculations. Newer versions can also perform energy assessments according to DIN V 18599 and EN 15193, as required for energy certificates. Dialux can also be used for planning tasks such as illuminating optimal illumination of artwork in a gallery.[1][2]​.

The software is available for free through the manufacturer's website. It was used, for example, in the lighting design for the Old Munich Pinakothek in Munich or for the Goslar Imperial Palace, a UNESCO World Heritage Site.[3]​[4]​.

DIAL was founded in 1989 as the German Institute for Applied Lighting Technology. Since then, the company has been dedicated to software development, lighting engineering, lighting planning and building automation. There are more DIAL offices in Italy, USA and Taiwan.

The first version of DIALux was released in 1994. The program was further developed over the following years and many new features were added until finally version DIALux 4.1 was created. DIALux evo was announced as the successor and was released for use in 2012. The DIALux evo version that was released then is based on a completely new graphics engine, a new interface and new functions. As many designers were still very accustomed to the previous version of the program, it could still be downloaded from the company's website for a while to facilitate the transition from DIALux 4 to DIALux evo. DIALux evo is now established and has many more features than the previous version. DIALux evo version 13.0 brings numerous new functions for the calculation of intrusive light. It is available in 26 languages ​​and has several hundred lighting manufacturers in its database.