Simon Kacsics, Count of the Székelys

Simon from the kindred Kacsics (Hungarian: Kacsics nembeli Simon; died after 1327) was a Hungarian lord at the turn of the 13th and 14th centuries, who served as Count of the Székelys from 1321 to 1327.

He was born into the Falkos (or Libercse) branch of the ancient gens (clan) Kacsics, as the son of Michael Kacsics (fl. 1271–1301) and an unidentified noblewoman from the so-called "Zólyom kinship", ancestors of the future powerful Balassa family. Simon had three siblings: his two brothers were Thomas the Fat ("Tompos"; fl. 1291–1309) and Peter the Bohemian (fl. 1291–1332), forefathers of the Tompos de Libercse and the Geréb de Vingárt families, respectively. Their unidentified sister married Reynold Kökényesradnót. From his unidentified marriage, Simon had two sons and a daughter: the eldest one Simon became the provost of Dömös (according to Pope John XXII's charter, he earned the office sometimes before November 1325) and court chaplain of Clementia of Hungary. The second son Rado was the ancestor of the Radó de Libercse noble family, which flourished until c. 1422. Simon's only unidentified daughter married Stephen III Losonci.

Simon first appeared in contemporary sources since 1291, alongside his brothers, on the occasion of their father's trial against his brother Farkas over landholding matters, regarding the Szécsény lordship. In addition, the brothers also filled a lawsuit against their mother's family to gain her rightful heritage, the so-called "daughter's quarta" (Latin: quartalitium). As a result, they acquired the villages of Halászi and Galábocs (today Glabušovce, Slovakia) in 1297.

As almost his whole kinship, Simon served as a familiaris of Matthew Csák, the powerful oligarch, who ruled de facto independently the north-western counties of the kingdom, including Nógrád and Hont counties, where the ancient estates of the Kacsics clan had laid. Only Simon's cousin Thomas supported King Charles I's efforts to defeat the oligarchs, as a result he lost all of his fortune and became penniless, and he could hope the recovery of his lost family landholdings and castles only from a successful restoration of the strong royal power by Charles. On 10 November 1308, Simon was one of the signatories of the treaty of Kékes, when papal legate Gentilis de Montefiori persuaded Matthew Csák to accept Charles's rule. Around 1310, he besieged and captured Nyitra Castle on behalf of Csák, causing serious damage in the walls. Following that he was appointed castellan of Nyitra, was mentioned in that capacity on 24 June 1317.