Sir William Lower (1570 – 12 April 1615)^[1] was an English astronomer from the early telescopic period, and a Member of Parliament.

He was born in Cornwall, and after studying at Exeter College, Oxford, he married and settled in South-west Wales. In 1607, he observed Halley's comet and took a number of careful measurements which he communicated to Thomas Harriot, by which it was determined that the comet was following a curved course. Lower suggested that the comet's orbit obeyed Kepler's laws (instead of being an atmospheric phenomenon or following a rectilinear path, as was generally thought at the time).

Using a telescope that had been provided by Harriot, Lower made a number of observations of the moon, and noted that its surface appeared irregular and "like a tart that my cooke made me last weeke". Similar observations were published by Galileo a few weeks later.

Lower represented Bodmin in the 1601 parliament, and Lostwithiel from 1604 to 1611. He was knighted in 1603.^[2]

Lower married Penelope Perrot, the daughter of Sir Thomas Perrot and Dorothy Devereux, by whom he had three sons and a daughter.^[3][4][5] After Lower's death Penelope (née Perrot) married secondly Sir Robert Naunton, by whom she had a daughter Penelope, who married Philip Herbert, 5th Earl of Pembroke.