Filipino architect Leandro Valencia Locsin (Silay1928 - Makati 1994) produced an architectural work that involved 250 projects, of which at least more than half were completed and mostly in his country of origin. A graduate in architecture of San Tomas de Manila University in 1953, his career began after the Second World War, which left the capital city all but destroyed following airstrikes by the allies that served to liberate the Philippines from the Japanese occupying forces. Following his studies, Locsin is immediately solicited with requests which leads him to open his office and give up the idea of completing his graduate studies in one of the prestigious American universities, which at the time had welcomed great masters who had sought exile from Europe to the United States in the 1930s. For a member of a privileged social class, this atypical career path makes Locsin a singular figure in the architectural landscape as he will immediately focus his interest on questioning the specificity of Filipino architecture. In a 1989 interview, Locsin confirms his career-long interest in researching the boundaries between local culture and international influences. The study of the vernacular tradition in his country will orient his work towards defining certain architectural principles to allow for the emergence of a new contemporary Filipino architecture. The post-war period, involving innovations in technical resources and favorable political and economic conditions for urban development, will serve to render all the more complex a body of work that is difficult to apprehend and qualify. In a 1964 text, Locsin refers to the elusive identity of the Filipino architectural spirit which, according to him, is the result of an assimilation of various external influences, given the geographic positioning of the Philippines and its colonial past. His work never ceased to reflect this quest for identity in built representations. While Leandro V. Locsin has been called "the poet of space" for the quality of his projects characterized by a great attention given to the sense of space, abstraction, symmetry, proportion, and materiality linked to the use of concrete and traditional materials his work has never been the subject of a complete study. Few scientific contributions exist and remain partial, in that they focus on certain specificities of his production. Further, there are no studies that offer a complete review of his office archives, a necessary step towards uncovering and highlighting the unique characteristics of a multiform production. The objective of this dissertation is to provide a complete overview of the work of Leandro V. Locsin, notably through a survey of his projects, and an analysis of the condition of their production in a local and international context, in order to render explicit the specific qualities that make this work a unique example of architecture of the period and from the Philippines.