Newton was a parliamentary borough in the county of Lancashire, in England. It was represented by two Members of Parliament in the House of Commons of the Parliament of England from 1559 to 1706 then of the Parliament of Great Britain from 1707 to 1800 and of the Parliament of the United Kingdom from 1801 until its abolition in 1832.

In 1885 a county constituency with the same name was created and represented by one Member of Parliament. This seat was abolished in 1983.

The borough consisted of the parish of Newton-le-Willows in the Makerfield district of South Lancashire. It was first enfranchised in 1558 (though the Parliament so summoned did not meet until the following year), and was a rotten borough from its inception: Newton was barely more than a village even at this stage, and so entirely dominated by the local landowner that its first return of members described it bluntly as "the borough of Sir Thomas Langton, knight, baron of Newton within his Fee of Markerfylde". By 1831, just before its abolition, the population of the borough had reached only 2,139, and contained 285 houses.

The right to vote was exercised by all freeholders of property in the borough valued at forty shillings or more, or by one representative of joint tenants of any such freeholds; Newton was the only borough where the forty-shilling freehold franchise (which applied in the counties) was the sole qualification to vote. In 1797, the borough's last contested election, 76 electors cast their votes; by 1831 it was estimated that the electorate had fallen to about 52. (As elsewhere, each elector had as many votes as there were seats to be filled and votes had to be cast by a spoken declaration, in public, at the hustings.)

In practice, however, the townsmen of Newton had no say in choosing their representatives: as the owners of the majority of the qualifying freeholds, the lords of the manor exercised total control. During most of the Elizabethan period, Langton seems to have allowed the Duchy of Lancaster to nominate many of the members, which may have been a quid pro quo for Newton's being enfranchised in the first place, but later patrons could regard its parliamentary seats as their personal property. Langton's heir sold the manor to the Fleetwood family in 1594, the sale explicitly including the right of "the nomination, election and appointment" of the two burgesses representing the borough in Parliament, one of the earliest recorded instances of the right to elect MPs being bought and sold. By the first half of the next century it had passed to the Leghs, who owned it for the rest of its existence.

By the time of the Great Reform Act of 1832, Newton was one of the most notorious of all England's pocket boroughs, mainly because the Legh control was more complete than that of the patrons in most other constituencies. It was one of the 56 boroughs to be totally disenfranchised by the Reform Act.

The Redistribution of Seats Act 1885 created a new Newton constituency, as one of twenty-three divisions of the parliamentary county of Lancashire.

• List of former United Kingdom Parliament constituencies
• Unreformed House of Commons