Piotr of Goniądz (Polish:Piotr z Goniądza,pronounced[ˈpʲɔtrzɡɔˈɲɔndza];Latin:Gonesius; c. 1525–1573) was a Polish political and religious writer, thinker and one of the spiritual leaders of thePolish Brethren.

Little is known of his early life. He was born to apeasant family some time between 1525 and 1530 in the town ofGoniądz. According toSymon Budny his true name wasGiezek, though throughout his life he used a variety of names and pseudonyms, including Gonesius, Gonedzius, Conyza and Koniński. He was sent by his parents to a monastery and became a Catholic priest.^[1] Supported by the bishop ofWilnoPaweł Holszański, Piotr was sent to Italy, where he graduated from theUniversity of Padua. There he received adoctorate inphilosophy and became one of the professors. However, following his lecture of the anonymous work byMiguel Serveto and similar works by an Italian professorMatteo Gribaldi, Piotr of Goniądz converted toProtestantism and returned to Poland.

One of the pioneers ofanabaptism in Poland, he was active as one of the notable members of theProtestant community formed aroundMikołaj Radziwiłł. It was he who contacted the anabaptists exiled from theGerman states who settled in large numbers inMoravia and convinced many of them to settle in Poland. He was also heavily influenced by the views of BohemianHussites, who supported modesty, life in poverty and disregard for mundane life. For his support ofunitarianism andanti-trinitarianism at the Protestant council ofSecemin (22 January 1556), he was officiallyexcommunicated by the Calvinists at theSynod of Pińczów in April of that year. He was also banished fromLesser Poland. However, he found several supporters of his ideas, mostly from among the lesserszlachta ofPodlaskie and the lands ofGrand Duchy of Lithuania. Probably in 1558 he found a benefactor and patron in person ofJan Kiszka, one of the most powerfulmagnates of his time. Invited toWęgrów, Piotr became the head of the local Protestant commune and one of the most notable leaders of theCalvinist community in Poland.

The radical political, ethical and religious beliefs of Piotr of Goniądz gained him much popularity among the Protestant clergy and lesser gentry, though also created many conflicts, especially with the magnates. Piotr supported egalitarianism, pacifism and disregard for mundane life. The members of his community, often regarded as a sect within the Calvinist church, were forbidden to hold any public office, serve in the army or even carry arms. Piotr also strongly opposedserfdom, which led to constant conflicts even with his patron.

In 1565 the schism within the Polish Calvinist church became a fact and Gonesius became a leader along withMarcin Czechowic and others of the so-calledEcclesia Minor, while the majority of Polish Protestants, theEcclesia Major, remained faithful to the much less radical beliefs ofJohn Calvin.

He died inWęgrów on 15 October 1573, during an outbreak ofplague.

The most notable of his works, theDe filio Dei homine Christo Iesu (translated asOn the Son of God, though literal translation would beOn the Son of God, a Human Jesus Christ), did not survive to our times.

Other of his notable works were published in 1570 in Kiszka's printing house in Węgrów. Among them wasDoktrina pura et clara de praecepuis Christianae religionis articulus, which survived in a single copy currently held inBibliothèque Nationale in Paris.

O ponurzaniu chrystiańskim (On Christian Baptism).

O trzech (OnTrinity).

• List of Poles

• Stanisław Kot (1957).Socinianism in Poland. The Social and Political Ideas of the Polish Antitrinitarians. Boston.
• Lech Szczucki, ed. (1983).Socinianism and its role in the culture of XVIth to XVIIIth centuries. Zbigniew Ogonowski,Janusz Tazbir. Warsaw-Łódź,PWN. p. 239.ISBN 83-01-03051-8.
• Zbigniew Ogonowski, ed. (1991).Myśl ariańska w Polsce XVII wieku; antologia tekstów. Wrocław-Lwów,Ossolineum. p. 649.ISBN 83-04-03588-X.
• J. Jasnowski (1935). "Piotr z Goniądza".Przegląd Historyczny.ISSN 0033-2186.