Commercially available light-emitting diodes (LEDs) suffer from low-efficiency in the green region of the visible spectrum. In order to solve this issue III-V materials such as Gallium phosphide (GaP) can be investigated. GaP in the zinc blende (ZB) crystal structure has an indirect band gap, limiting the efficiency of the green emission. However, when the material is grown with wurtzite (WZ) crystal phase a direct band gap is predicted. Here, we show the fabrication and the characterization of wurtzite GaP nanowires, together with the demonstration of the direct band gap. The strong photoluminescence signal observed at 594 nm with a lifetime in the order of 1ns matches with the expectation for a direct band gap material. Furthermore, the emission wavelength can be tuned across a wide range of the visible spectrum (555-690 nm) by incorporating aluminum or arsenic in the WZ GaP nanowires.