List of rulers of Austria
Divided rule

Name
Portrait
Birth
Marriages
Death
Leopold III the Just 1379–1386
-
1 November 1351 Vienna fourth son of Albert the Wise and Joanna of Pfirt
Viridis Visconti 23 February 1365 Vienna six children
9 July 1386 Sempach aged 34
William the Courteous 1386–1406
-
c. 1370 Vienna eldest son of Leopold the Just and Viridis Visconti
Joan II of Naples 13 November 1401 Vienna no issue
15 July 1406 Vienna aged 36
Leopold IV the Fat 1386–1411
-
c. 1371 Vienna second son of Leopold the Just and Viridis Visconti
Catherine of Burgundy 15 August 1393 Vienna no issue
3 June 1411 Vienna aged 40
Ernest the Iron 1402–1406
-
c. 1377 Bruck an der Mur third son of Leopold the Just and Viridis Visconti
(1) Margaret of Pomerania 14 January 1392 Bruck an der Mur no issue (2) Cymburgis of Masovia 25 January 1412 Kraków nine children
10 June 1424 Bruck an der Mur aged 47
Frederick IV of the Empty Pockets 1402–1406
-
c. 1382 fourth son of Leopold the Just and Viridis Visconti
(1) Elisabeth of the Palatinate 24 December 1407 Innsbruck one daughter (2) Anna of Brunswick 11 June 1411 Innsbruck four children
24 June 1439 Innsbruck aged 57

Question: Who succeeded Leopold III the Just as ruler of Austria when did he rule?
Answer: William the Courteous (c. 1370 – 15 July 1406) succeeded Leopold III the Just as the Duke of Austria from 1386 until his death in 1406.