Final answer:
Antonio Vivaldi is the most renowned and prolific Baroque composer of concertos, known for his over 500 concertos and famous work, 'The Four Seasons'.
Step-by-step explanation:
The most famous and most prolific Baroque composer of concertos is Antonio Vivaldi. Vivaldi, an Italian composer, violinist, teacher, and cleric, wrote over 500 concertos during the Baroque period. His best-known work is a series of violin concertos known as The Four Seasons. Vivaldi's influence was widespread across Europe, and his musical style emphasizes melody and a distinctive use of rhythms, harmonies, and forms that are characteristic of the Baroque period.