Lady Xu (徐氏, personal name unknown, 917–940), better known as Princess Yongxing (永興公主), was the fourth daughter of Li Bian (known as Xu Zhigao or Xu Gao during her life), the usurper who seized power from the Wu dynasty ruling house to found the Southern Tang dynasty. Princess Yongxing had married the Wu crown prince Yang Lian, and after the usurpation in 937 she stayed loyal to him even though she was elevated to a princess while he was demoted to "Commandery Duke of Hongnong". It has been said that she inevitably started crying every time people mentioned her by the new title "princess", conferred by her father, much to the chagrin of her older brother Li Jing (then known as Xu Jing). Her father reportedly called her a "good wife". When Yang Lian was banished to Chi Prefecture, she followed him there. She died "without an illness" shortly after her husband died under suspicious circumstances (likely murdered by her father).

永興公主（917年 - 940年），是中國五代十國南唐開國皇帝烈祖李昪第四女。

她在吳國天祚三年（937年）正月成為吳帝楊溥的太子楊璉的太子妃。李昪取代吳國，建立齊國。冊封永興公主。宋齊丘請公主離婚，李昪不許。她聽到別人稱呼自己為公主，非常悲傷。隨楊璉到池州。940年，楊璉從平陵回京的時候，在船里大醉暴亡。公主回金陵，自稱未亡人，在佛前祈禱：「願兒生生世世莫作有情之物」。二十四歲，無疾而終。