Some of the earliest known guitar-like instruments include the Middle Eastern oud, which dates back to around 1000 AD, and the European vihuela, which emerged in the 15th century. These instruments had many features in common with the modern guitar, such as a fretted neck and a soundboard, but they also had some key differences, such as the use of different materials and construction methods.
The earliest known instrument that is specifically identified as a "guitar" is the Spanish vihuela de mano, which emerged in the 15th century. The vihuela de mano was a plucked string instrument with a distinctive body shape and a wide range of tuning options. It played an important role in Spanish music and was considered a sophisticated and versatile instrument.
Over the centuries, the guitar underwent various changes and modifications, giving rise to different types of guitars, including the classical guitar, the acoustic guitar, and the electric guitar. The guitar gradually gained popularity as a solo instrument, an accompaniment instrument, and a vital component in many musical genres.
In summary, while it is difficult to pinpoint a single instrument as the "first guitar" with absolute certainty, the guitar's history can be traced back several centuries to various guitar-like instruments in different parts of the world. Instruments such as the Middle Eastern oud, the European vihuela, the Spanish vihuela de mano, and their subsequent developments over time are considered milestones in the evolution of the guitar as we know it today.