Thomas Baylies (1687–1756) was a Quaker ironmaster first in England, then in Massachusetts.
Thomas Baylies was the son of Nicholas Baylies of Alvechurch in north Worcestershire. On 5 June 1706, he married Esther, daughter of Thomas Seargeant of Fulford Heath, in Solihull in a Quaker ceremony at which 38 witnesses were present. They had eight children. Esther's sister Mary married Abraham Darby I.
By 1714, Baylies had joined his brother-in-law, Abraham Darby, at his Coalbrookdale ironworks, becoming a partner with him and John Chamberlain. Together they built a second blast furnace at Coalbrookdale and secured the rights to build a furnace at Dolgûn near Dolgellau and taking over Vale Royal Furnace in 1718. However, Darby died in July 1717, before any progress was made with either project, and the partnership was dissolved.
Baylies took over the Coalbrookdale Company's right to Vale Royal. Lacking sufficient capital, he formed a new partnership with Charles Cholmondeley of Vale Royal Abbey, Richard Turner of Pettywood and William Watts of Newton near Middlewich. Turner was concerned in a coal mine at Thatto Heath near St Helens and persuaded his partners to build a furnace at Sutton (there). They also built a forge at Acton Bridge and intended to (but perhaps did not) build another at Dean Mill in Haydock. Baylies moved to Marton near the works. The original capital of £5000 was doubled when the second furnace was planned. Baylies had difficulty in paying up the capital of his share, now reduced to one-sixth, because it was still tied up in the stock at Coalbrookdale. His difficulties were made worse by Mary Darby's death following soon after that of her husband. The company suffered substantial losses, forcing Cholmondeley to make an assignment of his estate for the benefit of his creditors, blaming his troubles on the obstinacy of Dick Turner.