Solar cycle 9 was the ninth solar cycle since 1755, when extensive recording of solar sunspot activity began. The solar cycle lasted 12.4 years, beginning in July 1843 and ending in December 1855. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 131.9 (February 1848), and the minimum was 3.2. There were a total of approximately 654 days with no sunspots during this cycle.
Solar cycle 9 began in 1843, the year that Heinrich Schwabe discovered the sunspot cycle. During this cycle, Edward Sabine, Rudolf Wolf, and other scientists recognized that solar disturbances affected the Earth's magnetic environment, so that solar cycles are identical to the Earth's geomagnetic cycles. Wolf also introduced the Wolf number during this period.
Geomagnetic activity during solar cycle 9 followed a double-peaked distribution, with more magnetic storms during the rising (1847–48) and falling (1851–54) parts of the cycle.