Solar cycle 1 was the first solar cycle since extensive recording of solar sunspot activity began. The solar cycle lasted 11.3 years, beginning in March 1755 and ending in June 1766. The maximum smoothed sunspot number (monthly number of sunspots averaged over a twelve-month period) observed during the solar cycle was 86.5 (June 1761), and the minimum was 11.2.
Cycle #1 was discovered by Johann Rudolph Wolf who, inspired by the discovery of the solar cycle by Heinrich Schwabe in 1843, collected all available sunspot observations going back to the first telescopic observations by Galileo. He was able to improve Schwabe's estimate of the mean length of the cycle from about a decade to 11.11 years. However, he could not find enough observations before 1755 to reliably identify cycles, hence the 1755–1766 cycle is conventionally numbered as cycle #1. Wolf published his results in 1852.