The year 1720 in science and technology involved some significant events.

• February 10 – Edmond Halley is appointed as Astronomer Royal of England.

• May – First patient admitted to the Westminster Public Infirmary, predecessor of St George's Hospital, London.
• Dr Steevens' Hospital is established at Kilmainham, Dublin. ^[1]
• Great Plague of Marseille, the last major outbreak of bubonic plague in Europe.
• English physician Richard Mead publishes A Short Discourse concerning Pestilential Contagion, and the Method to be used to prevent it.

• Willem 's Gravesande publishes Physices elementa mathematica, experimentis confirmata, sive introductio ad philosophiam Newtonianam, an introduction to Newtonian physics, in Leiden.

• A theodolite is developed by Jonathan Sisson of England.
• Pinchbeck is invented by English watchmaker Christopher Pinchbeck; it is an alloy of 83% copper and 17% zinc, creating a strong, hard-wearing metal which has the appearance and weight of 20 carat gold.
• An early chronograph is invented which has only mechanical parts in it.
• Henry de Saumarez (of the Channel Islands) produces an instrument called the Marine Surveyor intended to measure a ship's velocity. ^[2]
• A single-action five- pedal harp is developed by Jacob Hochbrucker of Bavaria which can raise the pitch of the selected strings by a half step.
• approx. date – Joseph Williamson uses a differential gear in a clock.

• January 30 – Charles De Geer, Swedish industrialist and entomologist (died 1778)
• March 13 – Charles Bonnet, Genevan naturalist and philosophical writer (died 1793)
• July 18 – Gilbert White, English naturalist (died 1793)
• October 8 – Geneviève Thiroux d'Arconville, French novelist, translator and chemist (d. 1805)
• November 5 - Jean Baptiste Christophore Fusée Aublet, French pharmacist and botanist (died 1778)
• December ? – James Hargreaves, English inventor (died 1778)
• approx. date – Dmitry Ivanovich Vinogradov, Russian chemist and (died 1758)

• December 29 – Maria Margarethe Kirch, German astronomer (born 1670) ^[3]
• David Gregory, Scottish physician and inventor (born 1625)