The Castaways was a hotel and casino on the Las Vegas Strip in Paradise, Nevada. It began in the 1930s, as a small motel called Mountain View. It became the San Souci in 1939, and underwent several ownership changes in its early years. A hotel addition opened on August 21, 1955, when the property became the Sans Souci Hotel. A casino, showroom, and restaurant were eventually opened on October 23, 1957. These facilities closed less than a year later, due to financial problems, although the hotel continued operations. Following a bankruptcy reorganization, the shuttered facilities reopened in May 1960. However, the property soon closed due to further financial difficulties.

Investor Ben Jaffe purchased the Sans Souci and reopened it as the Polynesian-themed Castaways on September 1, 1963. A new signature attraction was a Jain temple replica referred to as the Gateway to Luck. Jaffe also added more hotel rooms. He served as landlord for the casino portion, which was operated by a separate group. The casino closed again in December 1964, and was briefly reopened a year later under a new operating group. Following another closure, it reopened in May 1967, and Jaffe sold the entire property later that year to Howard Hughes, marking his third Las Vegas casino purchase. Hughes owned it through Hughes Tool Company, and later through his Summa Corporation.

In 1986, casino owner Steve Wynn purchased the Castaways and nearby vacant property with plans to build a new resort on the land. The Castaways closed on July 20, 1987. Wynn's new resort, The Mirage, opened in 1989. The Castaways name would later be used for the Showboat Hotel and Casino on Boulder Highway, starting in 2001.

The property began in the 1930s, as a small motel called the Mountain View auto court. In 1939, it was sold to W. R. Miller and Dr. Freeman H. Smith, who renamed it the San Souci. They sold it to Burton Miller and his wife in 1941. The 16-room San Souci was sold again in 1946, to Las Vegas attorney H. Cleveland Schultz.

A grand opening for the renamed Sans Souci Hotel took place on August 21, 1955, following renovations which included a two-story, 82-room hotel and an Olympic-size swimming pool. Future additions were planned for the 12-acre property, including a casino, nightclub, and restaurant. The casino portion opened on October 23, 1957. It was operated by George E. Mitzell and Harold V. Hinds. The property also featured live entertainment in the new 400-seat Jamaica Room. At the end of 1957, Mitzell announced plans to add 100 additional rooms, although these did not materialize. In 1958, a meat company filed a $21,500 lawsuit against the Sans Souci for lack of payment. Saxophonist Charlie Ventura also filed a lawsuit, after suffering a fall on the casino's stage during a performance.

In July 1958, two Las Vegas men, Jerry Kastner and Arthur Rozen, agreed to invest a total of $75,000 in operating funds. Kastner ultimately purchased only $31,000 worth of casino stock, and later said that he pulled out of the deal because it had been misrepresented. The casino and showroom closed in August 1958, and the property filed for bankruptcy. Federal agents seized money from the Sans Souci for its failure to pay cabaret taxes. The hotel was unaffected. The Sans Souci later filed a $400,000 damages suit against Kastner, alleging that his pullout resulted in the property's bankruptcy. A court eventually ruled in Kastner's favor.

In 1959, a federal judge approved a reorganization plan which would include leasing the casino, showroom, restaurant and bar to a new group for five years, at $8,500 a month. The showroom reopened in May 1960, and the state approved the casino to add table games; it had only been licensed, the month prior, to operate slot machines. In August 1960, agents of the Internal Revenue Service seized 10 slot machines, which were considered contraband after the casino failed to purchase tax stamps.

The Sans Souci re-entered bankruptcy in November 1961, after four major creditors rejected financial negotiations. The property owned more than $900,000. It eventually closed and, in November 1962, was sold in a bankruptcy auction for $749,600. The new owner was Ben Jaffe, a Las Vegas investor and owner of the Tropicana.