The deliberate observation and viewing of sunspots with a telescope can be attributed to a single individual: Galileo Galilei, around 1610 to 1611. His detailed records and subsequent publication, Letters on Sunspots (1613), provided a crucial piece of evidence that the Sun is not a perfect sphere, which directly contradicted the Aristotelian view of the universe at that time. From these records, he also correctly deduced that the Sun rotates on its own axis.
Although other people, such as Thomas Harriot and Johannes Fabricius, also observed the presence of sunspots at approximately the same time, it can be said that the most influential and acknowledged observation can be attributed to Galileo.