FLOWPATH 2019, the 4th National Meeting on Hydrogeology, was held in Milan from 12th to 14th June 2019. According to the aim of the previous Editions of FLOWPATH, held in Bologna (2012), Viterbo (2014) and Cagliari (2017), the conference is an opportunity for Italian hydrogeologists to exchange ideas and knowledge on different groundwater issues. The objectives of the conference are: – To promote dialogue and exchange of scientific knowledge among young hydrogeologists; – To deepen the theoretical and practical aspects of our understanding on groundwater; – To update all the stakeholders, researchers and professionals on recent challenges in the hydrogeological sciences; – To encourage researchers, professionals and administrators to contribute to the improvement of water resources management. This Volume of Conference Proceedings contains the abstracts of oral and poster contributions accepted to FLOWPATH 2019. The abstract were evaluated by the Scientific and Organizing Committees. This volume contains 99 abstracts, submitted by Authors coming from Universities, Public Authorities and Private Companies of Italy and many other countries, such as Australia, Belgium, Croatia, Czech Republic, Greece, Hungary, Israel, Malta, Morocco, Nigeria, Spain, Switzerland, The Netherlands, U.K., and U.S.A. The conference focuses on four themes of great importance: 1. Groundwater Resource Management 2. Fractured Rocks and Karst Aquifers 3. Contaminated Sites 4. Urban Hydrogeology The content of the Conference Proceedings is organized according to the four topics of the conference. The keynote lectures open the sessions were they were presented, followed by the scientific contributions in alphabetical order by first author's family name.