Wetlands play an important role in the hydrologic cycle. This investigation was completed to determine the origin of waters and recharge-discharge areas using stable isotopes (δ18O and δD) which are fingerprints of the water in Güllük (Muǧla) wetland. This area is important both economically and in terms of aquaculture environment in Turkey. Sample locations were selected from not only wetlands but also the possible recharge area that consists of karstic springs and streams. EC (Electrical Conductivity) of the waters range between 5080-41000 μS/cm, except streams. δ18O and δD contents of the samples ranged from -6.00 to 0.50 and from -29.1 to 2.1, respectively. In general, samples plotted between Global and Local Meteoric Water line with waters also plotted on the seawater mixing line. The sources of salinity were evaluated by δ18O-Cl in and around the wetland. Streams are under the influence of "Evaporation"; samples from Avşar and Koruköy are under the influence of "Both Evaporation and Seawater Mixing"; Içme and Ekinambari springs, and Limni Lake are under the influence of "Seawater Mixing"; and Savran spring and Tuzla Lake are under the influence of "Dissolution of Salts-Leaching" processes. The fact that Savran source plotted in this area raises the question of whether the current sea water is the source of salinity. The recharge area of the wetland consists of karstic formations, sea water, streams and precipitation in the Güllük area.