John Visconti (died 1275) was the Judge of Gallura from 1238 to his death. He was a member of the Visconti

House of Visconti

Visconti is the family name of two important Italian noble dynasties of the Middle Ages. There are two distinct Visconti families: The first one in the Republic of Pisa in the mid twelfth century who achieved prominence first in Pisa, then in Sardinia where they became rulers of Gallura...

 dynasty of Pisa

Pisa

Pisa is a city in Tuscany, Central Italy, on the right bank of the mouth of the River Arno on the Tyrrhenian Sea. It is the capital city of the Province of Pisa...

.

John was the son of Ubaldo I Visconti

Ubaldo I Visconti

Ubaldo I Visconti was the de jure overlord of the Giudicato of Cagliari from 1217. He was a member of the Visconti family of Pisa, controlling Cagliari on behalf of his brother, who was judge jure uxoris from 1218....

 and cousin of Ubaldo of Gallura

Ubaldo of Gallura

Ubaldo II Visconti, son of Lamberto di Eldizio and Elena de Lacon, was the Judge of Gallura from 1225 to his death in 1238. He ruled every giudicato on the island of Sardinia at one point or another save Arborea....

. When the latter Ubaldo drew up a will in January 1237 at Silki

Silki

Şilki or Silki was a Bolgar ruler . Silki provided a policy of unification of Bolgar tribes. His son Almış was also a Bolgar ruler....

, John was nominated to succeed him. However, Enzo, the husband of his Ubaldo's widow Adelasia of Torres

Adelasia of Torres

Adelasia , eldest child of Marianus II of Logudoro by Agnes of Massa, daughter of William I of Cagliari, and successor of her brother, Barisone III, in 1236, was the Judge of Logudoro from 1236 and Judge of Gallura from 1238....

, seems to have taken control of both Gallura and Logudoro and was granted the title King of Sardinia by his father, the Emperor Frederick II. Nevertheless, John was soon in power in Gallura.

In 1254, he joined the Republic of Pisa

Republic of Pisa

The Republic of Pisa was a de facto independent state centered on the Tuscan city of Pisa during the late tenth and eleventh centuries. It rose to become an economic powerhouse, a commercial center whose merchants dominated Mediterranean and Italian trade for a century before being surpassed and...

 in her attack on John of Cagliari. In 1258, the Republic partitioned the Giudicato of Cagliari

Giudicato of Cagliari

The Giudicato of Cagliari was one of the four Sardinian giudicati of the Middle Ages. It covered the entire south and central east portion of the island and was composed of thirteen subdivisions called curatoriae. To its north and west lay Arborea and north and on the east lay Gallura and Logudoro...

 amongst her supporters. John annexed a third of it — Ogliastra, Quirra, Sarrabus, and Colostrai — to Gallura. John subsequently remained mostly on the Italian peninsula, participating in the wars between the Guelphs and the Ghibellines on the side of Pisa. He returned to the island in 1274, but was back in Pisa the next year, when he died there. All his possessions passed to the Republic.

He married Dominicata, daughter of Aldobrandino Gualandi-Cortevecchia, but she died in 1259. He married as his second wife a daughter of Ugolino della Gherardesca

Ugolino della Gherardesca

Count Ugolino della Gherardesca , count of Donoratico, was an Italian nobleman, politician and naval commander. He was frequently accused of treason and features prominently in Dante's Divine Comedy.-Biography:...

, Count of Donoratico. He was one of Ugolino's few supporters during the factional infighting which plagued Pisa. His son by Ugolino's daughter, Ugolino, called Nino, succeeded him.