Michael Maurice O'Shaughnessy (May 28, 1864 - October 12, 1934) was an Irish-born civil engineer who played an important role in the urban planning and infrastructure of San Francisco in the early 20th century, including in the reconstruction from the 1906 earthquake and fire. Bor in County Limerick, O'Shaughnessy studied civil engineering at several institutions, ultimately graduating from the Royal University of Dublin. While looking for a job in London, he was encouraged to try moving to California instead, which he did, arriving in San Francisco in March 1885. Unable to find work in San Francisco, he instead found employment planning cities and towns further in the interior of northern and central California, experience that would late prove helpful in determining a reliable water supply for San Francisco. By 1891, O'Shaughnessy had begun engineering projects in San Francisco itself, but still also worked elsewhere, including a stint in Hawaii, where he designed irrigation systems for sugar plantations. In 1912, O'Shaughnessy became city engineer for San Franciso, accepting a significant pay cut for the opportunity to shape several projects, including securing drinking water for the city (working with the private Spring Valley Water Co. and the Hetch Hetchy Project, building a dam and reservoir near Yosemite and channeling the resulting water to the city), the Geary Street Railway (an early component in the city's electric streetcar network), multiple tunnels through San Francisco's hills for streetcars, and various infrastructure and reconstruction projects related to roads, sewers, electricity, gas lines, and so on. O'Shaughnessy served as city engineer until 1932, when he took on an advisory role until his death two years later. He left a deep imprint on the city's layout and infrastructure. Multiple sites, including the dam at Hetch Hetchy, are named in his honor.