Eva Catharina Lessing (22 March 1736 – 10 January 1778) was a German woman of letters. She was born Eva Catharina Hahn on March 22, 1736 in the southern German city of Heidelberg. In 1756 she married the Hamburg businessman Engelbert König, giving her the married name Eva König. It was in 1767 that she first became friends with the playwright Gotthold Ephraim Lessing, who was also godfather to her son Fritz. After her husband König died in 1768, Eva was looked after by Lessing. In 1771 they became engaged, though circumstances did not favour a timely marriage. In fact, due to matters related to König's estate, Eva was obliged to make several visits to Vienna, over a lengthy period of time, and then accompany the young Prince Leopold of Brunswick-Wolfenbüttel, a future Prussian general, on a journey to Italy in 1775. As a result, the couple's main mode of contact during their engagement was through written correspondence, much of which has survived. In 1776 they were finally married, in Jork near Hamburg. Eva Lessing then moved to Wolfenbüttel with her husband. She died there, aged 41, in 1778, of neonatal sepsis soon after the birth of their son Traugott.