Biela's Comet or Comet Biela (official designation: 3D/Biela) was a periodic Jupiter-family comet first recorded in 1772 by Montaigne and Messier and finally identified as periodic in 1826 by Wilhelm von Biela. It was subsequently observed to split in two and has not been seen since 1852. As a result, it is currently considered to have been destroyed, although remnants have survived for some time as a meteor shower, the Andromedids.

The comet was first recorded on 8 March 1772 by Jacques Leibax Montaigne; during the same apparition it was independently discovered by Charles Messier. It was also recorded in 1805 by Jean-Louis Pons, but was not recognized as the same object. Around 9 December 1805 comet Biela passed about 0.0366 AU (5.48 million km) from Earth. After the 1805 apparition a number of attempts were made by Gauss (1806) and Bessel (1806) to calculate a definitive orbit. Gauss and Olbers both noted a similarity between the 1805 and 1772 comets but they were not able to prove a link.

It was Wilhelm von Biela, an army officer serving at the fortress town of Josefstadt, who observed the comet during its 1826 perihelion approach (on February 27) and calculated its orbit, discovering it to be periodic with a period of 6.6 years. At the time it was only the third comet known to be periodic, after comets 1P/Halley and 2P/Encke. The comet was named after Biela, although there was initially some controversy due to a later but independent discovery by Jean-Félix Adolphe Gambart, who also provided the first mathematical proof linking the 1826 and 1805 comets (letters from Biela and Gambart were published in the same issue of the Astronomische Nachrichten). A third claim was made by Thomas Clausen, who had independently linked the comets.

Olbers in 1828 predicted that in 2500 years, a collision with earth was probable. This became the framing story of The Year 4338: Petersburg Letters.

The comet appeared as predicted during its 1832 apparition, when it was first recovered by John Herschel on 24 September. The orbital elements and ephemeris calculated by Olbers for this return, and updated by Marie-Charles Damoiseau to take into account the gravitational effects of the planets, created something of a popular sensation, as they showed that the comet's coma would likely pass through the Earth's orbit around October 29, but at an Earth distance of about 0.55 AU (82 million km). Subsequent predictions, in the media of the time, of the Earth's likely destruction overlooked the fact that the Earth itself would not reach this point until November 30, a month later, as pointed out by François Arago in an article designed to allay public fears. He put the probability of collision to 1/281 million, though admitted that the comet tail gases may cause "the death of all animals, or produce epidemics".

Despite this, the fact that Biela's Comet was the only comet known to intersect the Earth's orbit was to make it of particular interest, both to astronomers and the public, during the 19th century.

In 1832, Greek-Austrian astronomer Georgios Konstantinos Vouris published his own calculations of the elliptical orbit of the comet entitled: Elliptical orbit calculation of Biela's Comet from 96 observations of the year 1832 (Elliptische bahnbere chung des Biela'schen cometen aus 96 beobachtungen des Jahres 1832). His article was a comprehensive overview of the elliptical orbit of Biela's Comet.

The 1839 apparition was extremely unfavourable and no observations were made as the comet never came closer than 1.8 AU from Earth since the comet was on the other side of the Sun. During 1839 the comet never had a solar elongation greater than 50 degrees.