The present disclosure relates to illumination or lighting assemblies and systems that provide illumination using LEDs. In one aspect, the present disclosure provides a lighting assembly, comprising: multiple light emitting diodes that emit light; an optical system that directs the light emitted by the light emitting diodes, the optical system positioned adjacent to light emitting diodes; and a cooling fin including a two-phase cooling system, the cooling fin positioned adjacent to the light emitting diodes such that the two-phase cooling system removes heat from the light emitting diodes. In another aspect, the present disclosure provides a lighting system including multiple lighting assemblies. The lighting assemblies and systems of the present disclosure can be used in, for example, a street light, a backlight (including, for example, a sun-coupled backlight), a wall wash light, a billboard light, a parking ramp light, a high bay light, a parking lot light, a signage lit sign (also referred to as an electric sign), static signage (including, for example, sun-coupled static signage), illuminated signage, and other lighting applications.