Galileo Galilei (1564-1642) was an Italian scientist, mathematician, and astronomer. He is best known for his pioneering observations and discoveries in the field of astronomy. Galileo made significant advancements in the use of telescopes for astronomical observations, allowing him to observe and document celestial bodies and phenomena. He discovered the four largest moons of Jupiter, known as the Galilean moons, and observed the phases of Venus, supporting the heliocentric model of the solar system proposed by Copernicus. Galileo's observations and support for heliocentrism challenged the prevailing geocentric view supported by the Catholic Church, leading to conflicts and controversies with the religious authorities of his time. His work laid the foundation for modern observational astronomy and had a profound impact on our understanding of the universe. Galileo's scientific contributions and advocacy for empirical evidence and reasoning continue to be celebrated in the scientific community.