Castelnuovo Don Bosco, formerly Castelnuovo d'Asti (Piedmontese: Castelneuv d'Ast) is a comune (municipality) in the province of Asti in the Italian region Piedmont, located about 20 kilometres (12 miles) east of Turin and about 25 kilometres (16 miles) northwest of Asti, on a hill near the confluence of the Nevissano and Bardella.

Castelnuovo Don Bosco borders the following municipalities: Albugnano, Buttigliera d'Asti, Capriglio, Moncucco Torinese, Moriondo Torinese, Passerano Marmorito, and Pino d'Asti.

Castenlnuovo's origins, as attested by the name (meaning "New Castle") are connected to a castle built before 1000 AD, around which a burgh grew as time passed. It was once divided in two by the lords of Riva and the counts of Biandrate, until it was given by the German emperors to the marquesses of Montferrat. Subsequently, it was under the commune of Asti, then a fief of the lords of Rivalba and of those of Piea, until it returned to Montferrat. Later it was acquired by the house of Savoy. It was a fief of the Simiana until the late 18th century.

It was named Castelnuovo d'Asti, prior to being renamed in honor of John Bosco. The renaming took place in 1929, after John Bosco's beatification.

In the frazione of Mondonio are the notable Castello di Rivalba, with a large square tower, and a Baroque parish church.