FSL-MRS is a new Python-based MRS fitting tool. The model is based on a linear combination of basis spectra, and fitting is achieved with a sampling approach which gives full posterior distributions of fitted parameters. Results are stored both as text files and an interactive HTML report. On publication the tool will be open source and free as part of the FSL package. The tool will be developed to handle MRSI and model fMRS as time-series. Here we demonstrate an initial implementation in phantom data and three brain regions of 37 subjects and compare against another fitting software.