This paper reports the development of a low-cost, portable, light-emitting diode (LED)-based ultraviolet (UV) exposure system. The major system components include UV-LEDs, a microcontroller, a digital-to-analog converter, and LED control circuitry. Through its front panel with a liquid crystal display and keypad, the UV-LED lithography system is able to receive user-defined values for exposure time and power, which allows the exposure dose to be tunable on demand. Compared to standard mask aligners, the UV-LED lithography system is a fraction of the cost, is simpler to construct using off-the shelf components, and does not require a complex infrastructure to operate. Such a reduction in system cost and complexity renders UV-LED lithography a perfect candidate for microlithography with large process windows typically suitable for MEMS, microfluidics applications.