Elizabeth Wyndham (née Ilive or Iliffe; c.1769[1] – 30 December 1822),[2] styled the Countess of Egerton after 1801, was an English polymath.

The children born to the couple prior to their marriage were: In 1798, Elizabeth Ilive submitted to the Royal Society of Arts the design for a "cross-bar lever" that she had invented, for the purpose of lifting stones.

[9] A portrait of Elizabeth, by Thomas Phillips, RA, is held at her former home, Petworth House.

[3] The artist William Blake lived near Petworth for a while, and Elizabeth is thought to have commissioned several works from him.

[12] Evidence for this includes the existence of receipts for artists’ supplies, glass and earthenware retorts, imploding bottles, Magdeburg hemispheres, and yellow powder.