William Borrer FRS ( Henfield, Sussex, 13 June 1781 – 10 January 1862) was an English botanist noted for his extensive and accurate knowledge of the plants of the British Islands.

[1] He travelled extensively around Britain to see and collect plants and lichens, and also once crossed the English Channel to visit Normandy.

These included Isnardia palustris at Buxted in 1827 and the grass Leersia oryzoides at Henfield Levels in 1844 and several willows.

[3] Borrer published very little in his own name but contributed information to several important works on British botany during the early 1800s that acknowledged his assistance.

In 1813 he began to work with Dawson Turner on British lichens and the Lichenographia Britannica was finally published in 1839.

He contributed to numerous other publications such as descriptions of lichens, Salix, Rosa, and Rubus to the supplement to English Botany published in 1830.

[2] His extensive annotated herbarium is conserved at the Royal Botanic Gardens, Kew and his correspondence is held in several archives, including Cambridge University Library.

[6] Several plant species were named after him, including Borrer's salt marsh grass, Glyceria borreri (Bab.)