Rancho Punta de los Reyes Sobrante was a 48,189-acre (195.01 km2) Mexican land grant in present-day western Marin County, California, given by Governor Manuel Micheltorena in 1843 to Antonio Maria Osio.
In 1839, Osio bought Rancho Punta de los Reyes from Joseph Snook (1798–1848), and sought about acquiring the adjacent eleven square league Rancho Punta de los Reyes Sobrante, which Governor Micheltorena granted him in 1843.
After Osio was granted Rancho Punta de los Reyes Sobrante, he built a few structures, but didn't spend much time there.
In 1843, when Rafael Garcia moved onto part of the neighboring Rancho Punta de los Reyes of James Richard Berry; Berry, in turn, moved west onto a portion of Osio's Rancho Punta de los Reyes Sobrante.
Joseph Hetherington a creditor undertook to force payment by hounding him on every occasion with insults and threats.
With the cession of California to the United States following the Mexican–American War, the 1848 Treaty of Guadalupe Hidalgo provided that the land grants would be honored.