The recently installed Stable Isotope Laboratory (SIL) of the Department of Geology at the University of Lisbon (GeoFCUL) was designed to serve the research needs of Earth and Environmental studies. This new facility is about to be inaugurated. The stable isotope laboratory is part of the "GEOLABS, Geosciences Laboratory Cluster” located at the Faculty of Sciences of the University of Lisbon, and runs under the supervision of the Research Units CeGUL and CREMINER-LARSyS.It will provide accurate analytical results for:oxygen, carbon, hydrogen and nitrogen isotopes and/or elemental analysis in water, minerals, soils and rocks. These data represent a major value both in technical and research approaches, with particular emphasis on those focused on understanding the interactions between the major reservoirs of the atmosphere, hydrosphere and lithosphere and its environmental implications, such as:1) pollution sources (soil contamination by mining and landfills; water resources),2) metallogenesis problems (signatures of hydrothermal alteration: metallic mining resources), 3) identification of fluids of different origins, 4) climatic studies (chataracterization of palaeoenvironmental; CO2 resources and flow analysis of carbon dioxide and its climatic consequences),5) identification of mixing processes, 6) identification of salinization ( intrusion recent/ancient or dissolution of evaporites: water-rock interaction), 7) definition of preferencial recharge areas,just to name a few examples.SIL constitutes the first Portuguese laboratory devoted to the analysis of O, H and C isotopes in geological materials. A laser fluorination line, able to produce O isotope data out of very small samples of silicate and oxide minerals (<100 μm) is planned to be fully installed in a short time. The SIL is equipped with an IRMS spectrometer operating in DI- or in CF- modes and is hyphenated with an Isocarb and a Multiflow for analysis of carbonate minerals and/or rocks and O and H in waters, providing C, O, H data with high levels of analytical precision. Isocarb and Multiflow use very small samples <100 μg and have suitable precision for foraminifera analysis. A pioneering system for monitoring the temperature during the phosphoric acid etching of carbonate mineral mixtures allows sequential semi-automatic extraction of carbon from the different carbonate phases. SIL includes also an elemental analyser (EA) and gas chromatograph (GC). The new stable isotope laboratory at the University of Lisbon is a modern analytical facility designed to offer high-quality results both to research and applied-oriented studies.