Robert Thomas Livermore, also known as Don Roberto Livermore, (c. 3 November 1799 – 14 February 1858) was an English-born Californian ranchero. He emigrated to Alta California in 1822, eventually becoming a Mexican citizen and a prominent landowner in the Bay Area.

He was born in Springfield, Essex in England, to Robert Livermore and Mary Cudworth. Livermore was a stonemason's apprentice as a youth. At the age of 17, he decided to go to sea, joining the crew of an English merchant ship. Arriving in Baltimore, Maryland, he enlisted in the United States Navy and traveled to South America. He subsequently was part of Lord Cochrane's crew in 1820 during the Peruvian War of Independence against Spain. After Peru, he signed on with an English trading ship bound for California.

In 1822, he deserted from his ship in San Pedro, where he met another British ship-jumper - the Scot John Gilroy (namesake of the city of Gilroy). At that time, there were only a handful of English-speakers in Alta California, and Livermore probably also met the American Joseph John Chapman.

Livermore worked for a time at Mission San Gabriel and then moved north, working as the mayordomo (ranch foreman) at Rancho Bolsa del Potrero y Moro Cojo of Joaquín de la Torre, near Castroville. On 20 June 1823, Robert was baptized at the Mission Santa Clara into the Catholic faith, given the name Juan Bautista Roberto y José. At about the same time, in Monterey, he requested and was given permission by Governor Pablo Vicente de Solá to remain in California.

In 1834 Livermore and his business partner José Noriega were keeping livestock at Rancho Las Positas, where they also built an adobe. They purchased half of the land grant from William Gulnac in 1837, and officially received the grant in 1839 (technically, the land was granted to Salvio Pacheco and then sold to Livermore, as he was not a Mexican citizen). The only other inhabitant of the area at the time, besides the Ohlone, was José Amador (his rancho was near the present city of Dublin), who received his land grant a short time earlier. Livermore and Amador both helped each other build their adobes.

On 5 May 1838, Livermore married the widow Maria Josefa de Jesus Higuera Molina (1815–1879), daughter of Jose Loreto Higuera, grantee of Rancho Los Tularcitos, at the Mission San José. Josefa's grandfather, Ygnacio Higuera had been a member of Gaspar de Portolà's Expedition Sancta in 1769 and had accompanied Juan Bautista de Anza in his expedition of 1775–76. They first settled in the Sunol Valley, but later moved to Las Positas, as he was making regular trips there to manage his rancho. Initially an adobe structure built by Livermore and Amador served as their house on the rancho. In 1850, a wooden two-story house was shipped around Cape Horn and became the Livermores' new home. Later the adobe structure was rented to Nathaniel Greene Patterson who used it as a small hotel, the first place of entertainment in the valley.

The rancho's economy was based on cattle, hides, and tallow, as well as agriculture. Livermore planted the first wine grapes in the area and today, the Livermore Valley is one of California's premier wine-growing regions.

Livermore studiously avoided involvement in politics, and all evidence indicates he got along well with both the Mexican and Anglo communities, even becoming a Mexican citizen in 1844. His only participation in the events surrounding the conquest of California was to help carry word from Commodore John Drake Sloat to John C. Frémont at Sutter's Fort that Monterey had been occupied by American forces, and that may have been partly motivated by the fact that Noriega had been captured during the Bear Flag Revolt and was being held at Sutter's Fort.