Paxton's Tower is a Neo-Gothic folly erected in honour of Lord Nelson. It is situated on a hilltop near Llanarthney in the Towy Valley, Carmarthenshire, Wales. It is a visitor attraction that can be combined with a visit to the nearby National Botanic Garden of Wales. Its hilltop location provides views over the Botanic Gardens and the Towy valley. The tower is under care of the National Trust for Places of Historic Interest or Natural Beauty and is a grade II* listed building. 
The tower was built by Sir William Paxton (1745-1824), a Scottish-born but London-raised merchant and banker, whose forefathers were from Auchencrow by Paxton, Berwickshire. Paxton made his first fortune while with the HEIC in Calcutta with Charles Cockerell, brother of the architect. He purchased the Middleton Hall estate about 1790 and built the tower circa 1806-1809. Designed by the architect Samuel Pepys Cockerell (1754-1827), Middleton Hall was destroyed by fire in 1931.
Paxton may have been inspired to build the tower by Nelson's death at Trafalgar. Whilst in the office of mayor of Carmarthen, he may have met Nelson in person. Marble tablets dedicating the tower to Nelson were located above the entrances to the tower.
The tower is 36 feet high. The lower part of the tower is triangular in shape with a turret at each corner. On the first floor there is a banqueting room. Coloured glass from one of the windows can now be seen in the Carmarthen Museum at Abergwili. On the second floor there is a hexagonal prospect room surrounded by roof terraces. The windows to the prospect room are now bricked up. There is currently public access to the first floor banqueting room via stairs in one of the corner turrets.
A piece of land at the nearby National Botanic Garden of Wales, named Paxton's View because of its views of the tower, features the sculpture Pi by Rawleigh Clay, which consists of a large metal hoop mounted by a twisted wooden structure. The hoop is designed so that it "frames" the view of Paxton's Tower, and as such has been described as a "viewing circle" for the tower.
- "The Nelson Monument (also known as Paxton's Tower)., Llanarthney". British Listed Buildings. Retrieved 20 December 2013.
- Jones, D. Middleton Hall.
- Oxford Dictionary of National Biography: William Paxton