BSE's benchmark index of 30 large, established companies — India's oldest stock market index, running since 1986.
The S&P BSE Sensex tracks 30 financially sound, well-established companies listed on the Bombay Stock Exchange, chosen to represent a cross-section of India's economy. It's narrower than the Nifty 50 (30 stocks vs 50) but moves in close lockstep with it, since most large-cap companies are listed on both exchanges.
The Sensex predates the Nifty by roughly a decade and remains the more recognized name internationally, even though the Nifty 50 now carries more derivatives trading volume.