Marazion (/mærəˈzaɪən/; Cornish: Marghasyow) is a town and civil parish on the shore of Mount's Bay in Cornwall, England, United Kingdom. It is 2 miles (3.2 km) east of Penzance, and the tidal island of St Michael's Mount is half-a-mile offshore. At low water a causeway links it to the town and at high water passenger boats carry visitors between Marazion and St Michael's Mount. Marazion is a tourist resort with an active community of artists who produce and sell paintings and pottery in the town's art galleries.

Marazion lies within the Cornwall Area of Outstanding Natural Beauty (AONB). On the western side of the town is Marazion Marsh, a RSPB reserve and a Site of Special Scientific Interest (SSSI). At the 2021 census the population of the parish was 1,483 and the population of the built up area was 1,326.

Remains of an ancient bronze furnace, discovered near the town, tend to prove that tin smelting was practised here at an early period. Marazion was not recorded in the Domesday Book of 1088.

A late 11th century charter attributed to Robert, Count of Mortain, granted lands and liberties to St Michael's Mount, including the right to hold a market on Thursdays. Although the charter was granted to St Michael's Mount, the market appears to have always been held on the mainland opposite the island. This market appears to be the origin of the name Marazion, coming from Marghasbighan (Parvum Forum, lit. "small marketplace") of the earlier charters and the Marghasyewe (Cornish: "Thursday Market") or Marketjew (Forum Jovis) of the later charters. It may be added that a Jewish origin has been erroneously ascribed to the place from the name Marketjew.

Richard, Earl of Cornwall, granted a further market charter in 1257 which provided that the three fairs, on the two feasts of St Michael and at Mid-Lent, and the three markets which had hitherto been held by the priors of St Michael's Mount on land not their own at Marghasbighan, should in future be held on their own land at Marchadyou. He transferred in fact the fairs and markets from the demesne lands of the Bloyous in Marazion to those of the prior.

To remedy the loss incurred by this measure Ralph Bloyou in 1331 procured for himself and his heirs a market on Mondays and a fair on the vigil, feast, and morrow of St Andrew at Marghasyon. In Leland's time the market was held at Marhasdeythyow (Forum Jovis), and both Norden (1582) and Carew (1602) tell us that Marcajewe signifies the Thursday's market, which, whether etymologically sound or not, shows that the prior's market had prevailed over its rival.

Marazion was once a flourishing town, owing its prosperity to the throng of pilgrims who came to visit St Michael's Mount, but it largely ceased to be a place of pilgrimage at the Reformation. During the first half of the 16th century Marazion was twice plundered; first by the French in 1513, and later by Cornish rebels in 1549.

In 1595, Elizabeth I granted Marazion its own charter of incorporation, making it a borough. This ratified the grant of St Andrew's fair, provided for another on the Feast of St Barnabas and established a market on Saturdays. The corporation established by the 1595 charter consisted of a mayor, eight aldermen and twelve capital burgesses. Of the fairs, only the Michaelmas fair has survived and all the markets have gone.