A "shell beach" is a sea beach that routinely has an unusually large accumulation of seashells washed up on it. Seashells are most often the dead empty shells of marine mollusks, but may also include tests or shells of other kinds of marine animals.
The majority of beaches in the world are primarily composed of rock particles such as sand, grit, gravel, pebbles, etc, but in rare cases (including Shell Beach in Western Australia) a beach can be composed entirely of seashells, both broken and whole valves.
One area in the USA that is famous for its shell beaches is Sanibel Island on the Gulf Coast of Florida. In South Africa, the beaches of Jeffreys Bay are famous for shells, as is the Sulu Archipelago in the Philippines.
As a place name
The phrase "shell beach" has also become a place name for several areas which feature beaches rich in shells:
- Shell Beach, Pismo Beach, a neighborhood in San Luis Obispo County, California
- Shell Beach, La Jolla, a beach in San Diego County, California
- Shell Beach, Louisiana
- Shell Beach, Guyana, a sea turtle nesting beach
- Shell Beach, St. Mary's Island, Mangalore, India
- Shell Beach, Western Australia
- Barricane Beach, aka Shell Beach, just north of Woolacombe in North Devon, England 
Related names include:
- Shell Island (Wales), an island that has a long shell beach
The phrase "shell beach" has also been used in the following contexts:
- The name of a place in the movie Dark City
- Shell Beach (band), a Hungarian post-hardcore band named after the place in the movie