Augusta Leigh (1783-1851) was the half-sister of Lord Byron. They first started corresponding when Byron was at Harrow School and they maintained a close relationship until the death of Byron in 1824. Rumours of incest between the two surrounded the break-up of the marriage of Lord Byron with his wife, Anne Isabella Milbanke.

The letters here reflect their relationship and, as a result of her relationship with Byron, her relationships with his wider circle. There are here hundreds of letters of Augusta Leigh, the majority of which are to John Cam Hobhouse and John Murray [II]. Most of these letters refer to her half-brother. After the death of Lord Byron, Augusta Leigh writes of her own pecuniary circumstances, the posthumous reputation of her half-brother, and the selling of papers relating to Byron. In addition, there are letters to and relating to Augusta Leigh and of or relating to her family.