Securities Investor Protection Corporation (SIPC) is a nonprofit corporation established by the federal government that protects investor’s securities from harm if a broker/dealer defaults. 

In other words, it covers the replacement of missing securities up to $500,000, including $100,000 in cash if the firm where your brokerage account is held becomes insolvent or goes bankrupt. It does not protect from any potential loss while invested in the market and your brokerage firm must be a member of SIPC for you to be covered. 

For more information, visit SIPC.org