Giuseppe Melchiorre Sarto was born in Riese, Kingdom of Lombardy-Venetia, Austrian Empire (now Italy, province of Treviso) in 1835.
He was the second born of ten children of Giovanni Battista Sarto (1792–1852) and Margarita Sanson (1813–1894).
He was baptised 3 June 1835.
Giuseppe's childhood was one of poverty, being the son of the village postman.
Though poor, his parents valued education, and Giuseppe walked 3.75 miles (6.04 km) to school each day.

Giuseppe had three brothers and six sisters: Giuseppe Sarto (born 1834; died after six days), Angelo Sarto (1837–1916), Teresa Parolin-Sarto (1839–1920), Rosa Sarto (1841–1913), Antonia Dei Bei-Sarto (1843–1917), Maria Sarto (1846–1930), Lucia Boschin-Sarto (1848–1924), Anna Sarto (1850–1926), Pietro Sarto (born 1852; died after six months).
He rejected any kind of favours for his family; his brother remained a postal clerk, his favourite nephew stayed on as village priest, and his three single sisters lived together close to poverty in Rome, in the same way as other people of the same humble background lived.

At a young age, Giuseppe studied Latin with his village priest, and went on to study at the gymnasium of Castelfranco Veneto. "
In 1850 he received the tonsure from the Bishop of Treviso, and was given a scholarship [from] the Diocese of Treviso" to attend the Seminary of Padua, "where he finished his classical, philosophical, and theological studies with distinction".

On 18 September 1858, Sarto was ordained a priest, and became chaplain at Tombolo.
While there, Sarto expanded his knowledge of theology, studying both Thomas Aquinas and canon law, while carrying out most of the functions of the parish pastor, who was quite ill.
In 1867, he was named archpriest of Salzano.
Here he restored the church and expanded the hospital, the funds coming from his own begging, wealth and labour.
He became popular with the people when he worked to assist the sick during the cholera plague that swept into northern Italy in the early 1870s.
He was named a canon of the cathedral and chancellor of the Diocese of Treviso, also holding offices such as spiritual director and rector of the Treviso seminary, and examiner of the clergy.
As chancellor he made it possible for public school students to receive religious instruction.
As a priest and later bishop, he often struggled over solving problems of bringing religious instruction to rural and urban youth who did not have the opportunity to attend Catholic schools.

In 1878, Bishop Federico Maria Zinelli died, leaving the Bishopric of Treviso vacant.
Following Zinelli's death, the canons of cathedral chapters (of whom Sarto was one) inherited the episcopal jurisdiction as a corporate body, and were chiefly responsible for the election of a vicar-capitular who would take over the responsibilities of Treviso until a new bishop was named.
In 1879, Sarto was elected to the position, in which he served from December of that year to June 1880.

After 1880, Sarto taught dogmatic theology and moral theology at the seminary in Treviso.
On 10 November 1884, he was appointed bishop of Mantua by Leo XIII.
He was consecrated six days later in Rome in the church of Sant'Apollinare alle Terme Neroniane-Alessandrine, Rome, by Cardinal Lucido Parocchi, assisted by Pietro Rota, and by Giovanni Maria Berengo.
He was appointed to the honorary position of assistant at the pontifical throne on 19 June 1891.
Sarto required papal dispensation from Pope Leo XIII before episcopal consecration as he lacked a doctorate, making him the last Pope without a doctorate before Pope Francis.
Giuseppe Melchiorre Sarto was born in Riese, Kingdom of Lombardy-Venetia, Austrian Empire (now Italy, province of Treviso) in 1835. He was the second born of ten children of Giovanni Battista Sarto (1792–1852) and Margarita Sanson (1813–1894). He was baptised 3 June 1835. Giuseppe's childhood was one of poverty, being the son of the village postman. Though poor, his parents valued education, and Giuseppe walked 3.75 miles (6.04 km) to school each day.
Giuseppe had three brothers and six sisters: Giuseppe Sarto (born 1834; died after six days), Angelo Sarto (1837–1916), Teresa Parolin-Sarto (1839–1920), Rosa Sarto (1841–1913), Antonia Dei Bei-Sarto (1843–1917), Maria Sarto (1846–1930), Lucia Boschin-Sarto (1848–1924), Anna Sarto (1850–1926), Pietro Sarto (born 1852; died after six months). He rejected any kind of favours for his family; his brother remained a postal clerk, his favourite nephew stayed on as village priest, and his three single sisters lived together close to poverty in Rome, in the same way as other people of the same humble background lived.
At a young age, Giuseppe studied Latin with his village priest, and went on to study at the gymnasium of Castelfranco Veneto. "In 1850 he received the tonsure from the Bishop of Treviso, and was given a scholarship [from] the Diocese of Treviso" to attend the Seminary of Padua, "where he finished his classical, philosophical, and theological studies with distinction".
On 18 September 1858, Sarto was ordained a priest, and became chaplain at Tombolo. While there, Sarto expanded his knowledge of theology, studying both Thomas Aquinas and canon law, while carrying out most of the functions of the parish pastor, who was quite ill. In 1867, he was named archpriest of Salzano. Here he restored the church and expanded the hospital, the funds coming from his own begging, wealth and labour. He became popular with the people when he worked to assist the sick during the cholera plague that swept into northern Italy in the early 1870s. He was named a canon of the cathedral and chancellor of the Diocese of Treviso, also holding offices such as spiritual director and rector of the Treviso seminary, and examiner of the clergy. As chancellor he made it possible for public school students to receive religious instruction. As a priest and later bishop, he often struggled over solving problems of bringing religious instruction to rural and urban youth who did not have the opportunity to attend Catholic schools.
In 1878, Bishop Federico Maria Zinelli died, leaving the Bishopric of Treviso vacant. Following Zinelli's death, the canons of cathedral chapters (of whom Sarto was one) inherited the episcopal jurisdiction as a corporate body, and were chiefly responsible for the election of a vicar-capitular who would take over the responsibilities of Treviso until a new bishop was named. In 1879, Sarto was elected to the position, in which he served from December of that year to June 1880.
After 1880, Sarto taught dogmatic theology and moral theology at the seminary in Treviso. On 10 November 1884, he was appointed bishop of Mantua by Leo XIII. He was consecrated six days later in Rome in the church of Sant'Apollinare alle Terme Neroniane-Alessandrine, Rome, by Cardinal Lucido Parocchi, assisted by Pietro Rota, and by Giovanni Maria Berengo. He was appointed to the honorary position of assistant at the pontifical throne on 19 June 1891. Sarto required papal dispensation from Pope Leo XIII before episcopal consecration as he lacked a doctorate, making him the last Pope without a doctorate before Pope Francis.
Pope Pius X