Jan Alojzy Matejko was a Polish painter, a leading 19th-century exponent of history painting, known for depicting nodal events from Polish history. His works include large scale oil paintings such as Stańczyk (1862), Rejtan (1866), Union of Lublin (1869), Astronomer Copernicus, or Conversations with God (1873), or Battle of Grunwald (1878). He was the author of numerous portraits, a gallery of Polish monarchs in book form, and murals in St. Mary's Basilica, Kraków. He is considered by many as the most celebrated Polish painter, and sometimes as the "national painter" of Poland.

Matejko spent most of his life in Kraków. He enrolled at the Kraków Academy of Fine Arts at age fourteen, where he studied under notable artists such as Wojciech Korneli Stattler and Władysław Łuszczkiewicz and completed his first major historical painting in 1853. His early exposure to revolutions in Kraków and the military service of his brothers influenced his artistic themes. After studying art in Munich and Vienna, he returned to Kraków and set up a studio. He gradually gained recognition, selling key paintings that settled his debts and created some of his most famous works, including Stańczyk and Skarga's Sermon. Matejko's art played a key role in promoting Polish history and national identity at a time when Poland was partitioned and lacked political autonomy.

At the same time, Matejko's painting style has been criticised as old-fashioned and overly theatrical, labeled as "antiquarian realism". His works often lost their nuanced historical significance when displayed abroad due to the audience's unfamiliarity with Polish history. Matejko's support for the Polish cause was not just through his art; he also contributed financially and materially to the January Uprising of 1863. Later, he became director of the art academy in Kraków, which was eventually renamed the Jan Matejko Academy of Fine Arts. A number of his students became prominent artists in their own right, including Maurycy Gottlieb, Jacek Malczewski, Józef Mehoffer and Stanisław Wyspiański. He received several honors during his lifetime, including the French Légion d'honneur. Matejko was among the notable people to receive an unsolicited letter from the German philosopher Friedrich Nietzsche, as the latter tipped, in January 1889, into his psychotic breakdown while in Turin.

Matejko was born on 24 June 1838, in the Free City of Kraków. His father, Franciszek Ksawery Matejko (Czech: František Xaver Matějka) (born 1789 or 13 January 1793, died 26 October 1860), a Czech from the village of Roudnice, was a graduate of the Hradec Králové school who later became a tutor and music teacher. He first worked for the Wodzicki family in Kościelniki, Poland, then moved to Kraków, where he married the half-German, half-Polish Joanna Karolina Rossberg (Rozberg). Jan was the ninth of eleven children. His mother died when he was very young and his older brother, Franciszek had a hand in the manner of his upbringing. He grew up in a kamienica building on Floriańska Street. After the death of his mother in 1845, Jan and his siblings were cared for by his maternal aunt, Anna Zamojska.

At a young age he witnessed the Kraków revolution of 1846 and the 1848 siege of Kraków by the Austrians, two events which put an end to the Free City of Kraków. Two of his older brothers served in both armed conflicts, under General Józef Bem. One of them, Edmund, fell in battle and the other was forced into exile. Matejko attended St. Anne's High School, but he dropped out in 1851 because of poor grades. Matejko showed an early artistic talent, but had great difficulty with other academic subjects. He never fully mastered a foreign language. Despite that, and because of his exceptional skill, at the age of fourteen he entered the School of Fine Arts in Kraków, where he was a contemporary of Artur Grottger from 1852 to 1858. His teachers included Wojciech Korneli Stattler and Władysław Łuszczkiewicz. He opted for historical painting as his specialism, and finished his first major work, The Shuyski Tsars before Zygmunt III (Carowie Szujscy przed Zygmuntem III), in 1853 (he would return to this theme a year before his death, in 1892. During this time, he began exhibiting historical paintings at the Kraków Society of Friends of Fine Arts from 1855. His graduation project in 1858 was Sigismund I the Old ennobles professors of the Jagiellonian University (Zygmunt I nadaje szlachectwo profesorom Uniwersytetu Jagiellońskiego) and proved to be seminal.

After graduation in 1859, Matejko received a scholarship to study with Hermann Anschütz at the Academy of Fine Arts, Munich. The following year he received a further scholarship to study at the Academy of Fine Arts Vienna, but after only a few days and a major quarrel with Christian Ruben, Matejko returned to Kraków. He set up a studio at his family home in Floriańska Street. It took years before he met with commercial success. He struggled as the proverbial "starving artist", who finally celebrated when he managed to sell the Shuyski Tsars... canvas for five florins.

In 1860, against a background of cultural erosion in partitioned Poland Matejko published an illustrated album, Clothing in Poland (Ubiory w Polsce), a project reflecting his intense interest in the historical record of his nation and his desire to promote it among Polish people and incidentally stir their patriotism. His financial situation improved when he sold two paintings, The assassination of Wapowski during the coronation of Henri de Valois (Zabicie Wapowskiego w czasie koronacji Henryka Walezego, 1861) and Jan Kochanowski over the body of his daughter Urszulka (Jan Kochanowski nad zwłokami Urszulki, 1862), which settled his debts. 1862 saw the completion of his Stańczyk, initially received without much acclaim, but in due course becoming one of Matejko's best known works. It marks a manifest departure in Matejko's art, from mere illustrator of history to commentator upon its moral content.

During the January Uprising of 1863, in which he did not directly take part on account of his poor health, Matejko supported it financially, donating most of his savings to the cause, and personally transporting arms to an insurgents' camp. Subsequently, his Skarga's Sermon (Kazanie Skargi), May 1864, was exhibited in the gallery of the Kraków Society of Friends of Fine Arts, which gained him much publicity. On 5 November that same year, he was elected member of the Kraków Scientific Society (Towarzystwo Naukowe Krakowskie) in recognition for his contributions to depicting great national historical themes. On 21 November he married Teodora Giebułtowska, with whom he went on to have five children: Beata, Helena, Tadeusz, Jerzy and Regina. His daughter, Helena, also an artist, later helped World War I victims and was awarded the Cross of Independence by President Stanisław Wojciechowski.

After 1865 Matejko's international recognition grew. His Skarga's Sermon was awarded a gold medal at the 1865 Paris Salon, prompting Count Maurycy Potocki to buy it for 10,000 florins. In 1867, his painting Rejtan was awarded a gold medal at the World Exhibition in Paris and was acquired by Emperor Franz Joseph I of Austria for 50,000 franks. His next major painting was the Union of Lublin (Unia Lubelska), created during 1867–1869. Acclaimed in Paris, it won Matejko the Cross of the Légion d'honneur. and was purchased by the Sejm of Galicia. It was followed by Stefan Batory at Pskov (Stefan Batory pod Pskowem), finished in 1871. In 1872, he visited Istanbul and upon his return to Kraków finished The Astronomer Copernicus, or Conversations with God (Astronom Kopernik, czyli rozmowa z Bogiem), which was acquired by the Jagiellonian University. From the 1870s onwards he was aided by a secretary, Marian Gorzkowski, who became his personal assistant, his closest friend, a model for a number of his paintings, and the author of a memoir about Matejko.

In 1872, during an exhibition in Prague he was offered the directorship of the Prague Academy of Fine Arts, quickly followed by a similar offer from the Kraków School of Fine Arts. He accepted the Kraków position, and was for many years its principal (rector). In 1874, he finished Zawieszenie dzwonu Zygmunta (The Hanging of the Sigismund bell). In 1878, he produced another masterpiece, The Battle of Grunwald. That year he received an "honorary grand gold" medal in Paris, while Kraków city council presented him with a ceremonial scepter, as a symbol of his "royal status in fine art". In 1879 came his Rok 1863 - Polonia (The Year 1863 - Polonia), his depiction of the January Uprising. Begun in 1864 as the Uprising was waning, he abandoned the canvas for a number of years, perhaps due to the loss of several close friends and family members in the conflict. It languished unfinished until prince Władysław Czartoryski became interested in acquiring it. To this day it is considered unfinished.

1880-1882 were taken up with another large work, The Prussian Tribute (Hołd Pruski) which Matejko gifted to "the Polish nation". It earned him the honorary citizenship of Kraków. One of the city's squares was renamed Matejko Square. In 1883 he finished Jan Sobieski at Vienna (Jan Sobieski pod Wiedniem) which came to be presented to Pope Leo XIII as a "gift of the Polish nation". Being a member of the delegation delivering the canvas to Rome, Matejko was awarded the Knight Commander with Star of the Order of Pius IX. The painting is on permanent exhibition in the Sobieski Room at the Vatican Museums. Around that time he also became vocal on a number of political issues, publishing letters on topics such as Polish-Russian relations. He was also very engaged in efforts to protect and reconstruct historical monuments in Kraków. In 1886, he finished a painting relating to French rather than Polish history, The Virgin of Orléans, a portrayal of Joan of Arc.

In 1887 Matejko received an honorary doctorate from the Jagiellonian University, and recognition from the Austrian Society, Litteris et Artibus. In 1888 he completed The Battle of Racławice (Bitwa pod Racławicami). In 1888-1899, to justify his new academic title, he published a group of twelve drawings with accompanying commentary, The History of civilisation in Poland (Dzieje Cywilizacji w Polsce). Between 1890 and 1892, he published a series of works on paper, portraying all the monarchs of Poland (Poczet królów i książąt polskich - The kings and princes of Poland, including queens), whose popularity turned them into the canon portrayals of their subjects. 1891 marked his Constitution of the 3 May (Konstytucja 3 Maja). He went on to compose another large scale work, The Oaths of Jan Kazimierz (Śluby Jana Kazimierza), but death intervened. In 1892, a year before his death, he completed his Self-portrait (Autoportret).

In addition to the history paintings Matejko was a prolific portraitist. His subjects included Jagiellonian University rectors Józef Szujski and Stanisław Tarnowski, and numerous portraits of family and friends, including Wife in her wedding dress ("Żona w sukni ślubnej") (1865, destroyed by his wife during a quarrel and recreated in 1879) and a self-portrait (1892). Altogether Matejko authored 320 oil paintings and several thousand drawings and watercolours. He also designed the monumental polychrome murals for the Brick Gothic St. Mary's Basilica, Kraków (1889–1891), which in 1978 became a UNESCO World Heritage Site alongside the Historic Centre of Kraków.

Matejko suffered from a peptic ulcer, and died in Kraków on 1 November of internal bleeding. His funeral on 5 November drew large crowds, and his death was newsworthy in at least thirty two European newspapers. He was buried in Kraków's Rakowicki Cemetery.