Simi Adobe-Strathearn House, Historic adobe house in Simi Valley, United States.

The Simi Adobe–Strathearn House is a historic house museum in Robert P. Strathearn Historical Park in Simi Valley, California. Two rooms of the original adobe, the headquarters of Rancho Simi, survive within a Victorian residence built for Robert P. Strathearn in 1892–93. The house keeps period furniture and household displays.

Rancho Simi, also called Rancho San José de Nuestra Señora de Altagracia y Simi, was the earliest Spanish colonial land grant in Ventura and Santa Barbara Counties, covering 113,000 acres. Its headquarters stood here, and the house takes its name from Robert P. Strathearn, who built the 1892–93 residence. The Strathearn family kept the property until 1969, when the house and 5.85 acres were donated to the Simi Valley Recreation and Park District.

The house displays furnishings and objects from two distinct periods: the Spanish colonial era within the adobe rooms and the Victorian times of the Strathearn family. This side-by-side arrangement shows how life at this location evolved across generations.

The park is owned by the Rancho Simi Recreation and Park District and run with the Simi Valley Historical Society. Docent-led tours start at the Visitor Center, and building interiors can only be seen on these tours. Allow time to walk the grounds, where buildings moved from their original sites stand alongside the house.

Rather than demolishing the crumbling adobe structure, the Strathearn family integrated it into their new Victorian house and preserved two original adobe rooms. This unusual choice allows visitors today to see both building periods under a single roof.