Built in Greenwich, the Royal Observatory (f. 1675) was situated outside the capital but was deeply enmeshed within its knowledge networks and communities of practice. It was deeply reliant on London’s instrument makers, engaged with, and often produced, its teachers of navigation and mathematics, was an off-shoot of one government board and took a leading role on another, and was overseen by a Board of Visitors selected by the city’s Royal Society. This paper explores the extent to which the Observatory can be considered a London institution or, in its early years, as an institution at all. In particular, it considers ways in which its knowledge and practice were shared within and beyond its walls and argues that the Observatory’s proximity to London and its relationships with London institutions shaped its governance and the development of a particular, and ultimately influential, approach to astronomical and mathematical practice.