Gaetano Guadagnini II, born Andrea Gaetano Maria (1796 — 1852, Turin), was an esteemed Italian luthier renowned for crafting violins, guitars, and a variety of other stringed instruments. He was active in Turin from 1817 until his death in 1852, and he hailed from a distinguished lineage of luthiers. Gaetano was the eldest son of Carlo Pietro Antonio (1768—1816) and a nephew of Giuseppe Antonio Santo (1753—1805), as well as the grandson of the celebrated G.B. Guadagnini (ca.1711—1786).

Gaetano's luthier career commenced at an early age when, in 1817, he assumed control of the family workshop following the deaths of his father and uncle Gaetano I (1750—1817). Initially, his focus was on the repair and restoration of fine instruments, but he soon expanded his expertise to include the creation of guitars, achieving notable success in both plucked and bowed string instruments. His craftsmanship was recognized at the first Esposizione di Torino in 1829, where one of his guitars received a copper medal, lauded by jurors as sopraffina… eccellente ("superfine… excellent"). Guadagnini continued to garner accolades, winning a bronze award for his guitars and violins in 1838, and another for a pair of guitars in 1844. According to a posthumous inventory of his workshop, he also dealt in numerous antique bowed instruments, predominantly sourced from Mirecourt makers.

In the book "Giovanni Battista Guadagnini: The Life and Achievement of a Master Maker of Violins" (2000), author Duane Rosengard notes that Gaetano was the most successful entrepreneur within his family, elevating Casa Guadagnini to a level of critical acclaim and commercial success that surpassed previous generations. Italian organologist Emanuele Marconi characterized Guadagnini's business model as a "quasi-monopoly" in his article for Seicorde quarterly magazine (№83, April–June 2005). Marconi observed that Gaetano distinguished himself from other luthiers in 19th-century Turin through his commercial and organizational prowess, akin to the operations of the Fabricatore family in Naples. This included diversifying offerings to serve as a comprehensive resource for professional musicians, stocking a wide array of instruments from various makers along with gut strings and accessories. Additionally, he employed assistants and contracted other luthiers to enhance production under his brand.

Interestingly, Count Cozio di Salabue (1755—1840) noted in 1816 that Gaetano II had been engaged as a subcontractor for nobleman and luthier Alessandro D'Espine (1782—1855), during which Guadagnini varnished and decorated "white" decks for him.

The violins crafted by Gaetano II, with few surviving examples from the 1830s and 1840s, are characterized by their larger proportions and show minimal resemblance to the works of G.B. Guadagnini, reflecting a clear influence from contemporary French makers who were popular in Turin at that time. In his guitar production, he developed two distinct models: an earlier design reminiscent of his father's Baroque-inspired, pear-shaped decks, and a new model he created around 1821, which gained immense popularity and served as a template for subsequent generations of guitar-makers.

Throughout his career, Gaetano worked at two different locations, starting at Contrada della Palma, 16, until 1823, and then moving to Piazza St. Carlo, where he remained until his death. Following his passing in 1852, his son Carlo Antonio Maria Guadagnini (1831—1881) inherited the workshop. At least one of Gaetano's descendants, Francesco Carlo Filippo (1863—1948), continued the family tradition, passing the business down to his son and Gaetano II's great-grandson, Paolo Lorenzo (1908—1942). As a result, Casa Guadagnini endured for over two centuries across six generations, marking one of the longest-standing dynasties in classical Italian luthiery until World War II.