A trilateral agreement between ESO, the National Science Foundation (NSF) and the National Institutes of Natural Sciences (NINS), concerning the operation of ALMA was signed in Tokyo, Japan, on 15 December 2015. The contributions of the three international partners ensure the continued success of this transformational (sub-)millimetre observatory located on Chajnantor Plateau in northern Chile. The new agreement provides the framework for the long-term operations of ALMA over the next 30 years Tim de Zeeuw, ESO Director General (left), Katsuhiko Sato, NINS President (centre), and F. Fleming Crim, NSF Assistant Director (right, on behalf of France Córdova, NSF Director), represented the three partners at the ceremony and signed the ALMA Trilateral Agreement. Other staff members from ESO, the National Astronomical Observatory of Japan (NAOJ) and NSF were also in attendance.