Stiff Person Syndrome Awareness Day, also known as International Stiff Person Syndrome Awareness Day, is observed worldwide every March 15. This day was created to highlight Stiff Person Syndrome (SPS), a rare autoimmune neurological disorder characterized by progressive muscle rigidity and painful spasms. SPS affects approximately one or two in a million people, typically developing in middle age. The syndrome was first described in 1956 by neurologists Henry Woltman and Frederick Moersch, who initially referred to it as "stiff-man syndrome." The day gained significant attention in 2024 when Canadian singer Céline Dion, diagnosed with SPS, shared her experiences on social media. The main goal of this observance is to support patients and families affected by SPS and to emphasize the need for research into the condition.