Thelnetham Windmill, also known as Button's Mill is a Grade II* listed tower mill constructed of brick. The windmill is located at Thelnetham, Suffolk, England. It was built in the early nineteenth century to grind wheat into flour. Thelnetham windmill worked by wind power until 1924, latterly on two sails, after which it became derelict.

In 1979, a group of enthusiasts purchased Thelnetham windmill for restoration. Numerous volunteers helped to restore the mill to full working order over an eight-year period. The mill is open to the public, and flour ground at the mill can be bought at the site.

The mill is a small four storey tower mill with Patent sails and winded by a fantail. It drives two pairs of millstones, with a third pair driven by an auxiliary engine.

The earliest record of a windmill in Thelnetham was a post mill which was shown of Joseph Hodgkinson's map of Suffolk of 1778. In 1818, the post mill was moved to Sandy Lane, Diss, Norfolk

The post mill was replaced by a tower mill, which was built by millwright George Bloomfield for William Button in 1819. The mill was set to work on Christmas Day 1819. In 1832, the mill was modernised by the fitting of a cast-iron windshaft, Patent sails and a fantail. The new windshaft was fitted on 16 July 1832. It was made by J Aickman, the King's Lynn millwright, and weighs 1¾ tons (1,780 kg). A new stock was fitted in September 1836. William Button died on 11 February 1837. The mill passed jointly to his widow Rebecca and their son Richard. Richard Button worked the mill until 1860, at which date it was conveyed to his sons Richard and William, who sold it to Richard Peverett from Kenninghall, Norfolk in 1862.

The mill was worked by Stephen Peverett, Richard's son. He inherited the mill on the death of his father in 1875 and leased it to Henry Bryant in 1879. In 1884, the mill was sold by auction, and Henry Bryant purchased the freehold. Bryant rebuilt the floors of the mill. From 1892, a portable steam engine was used as auxiliary power, driving an extra pair of millstones on the ground floor. This was replaced in 1914 by a Hornsby oil engine. Bryant ran the mill until 1920 when he sold it to Alphonso Vincent, a retired millwright from Garboldisham, Norfolk. The Hornsby engine was sold in the early 1920s. The mill was tailwinded c1920, and as a result one pair of sails was removed. Vincent carried out some repairs to the mill and ran it until he retired in 1924. One of the remaining two sails was wrecked in 1926 when the mill was again tailwinded.

On the death of Alphonso Vincent in 1932, his son George inherited the property. He lived at the site in an old lorry until his death in 1973. The mill passed to his daughter, who sold it in 1974 to Mr and Mrs Humphries, who intended to convert it into a house. They later changed their minds and offered it for sale for restoration. In 1976, the cap of the mill was blown to pieces in a gale. Thelnetham windmill was purchased by five members of the Suffolk Mills Group in November 1979, and plans for restoration were made. The consortium consisted of Mark Barnard, Charles Dolman, Peter Dolman, David Pearce and Chris Seago. The derelict mill and an acre of land cost £6,000.

In 2013, the mill was gifted to the Suffolk Building Preservation Trust, which also owns Pakenham Watermill. On 14 July 2019, the bicentenary of the windmill was celebrated. The Locomobile lorry that George Vincent had lived in, now restored to its original army condition, was present. Also in 2019, the mill was used as a polling station during the European Parliament election in May, and in the General Election in December. The usual venue, Thelnetham Village Hall being unavailable due to it undergoing a major refurbishment.