Vanguard 500 Index Fund (the Fund) is an open-end investment company, or mutual fund. The Fund offers four classes of shares: Investor Shares, Admiral Shares, Signal Shares, and Exchange Traded Fund (ETF) Shares. The Fund seeks to track the investment performance of the Standard & Poor's 500 Index, an unmanaged benchmark representing the United States large-capitalization stocks. The Fund employs a passive management-or indexing-investment approach designed to track the performance of the Standard & Poor's 500 Index. The Fund attempts to replicate the target index by investing all, or substantially all, of its assets in the stocks that make up the index, holding each stock in approximately the same proportion as its weighting in the index.