Katherine Olivia Sessions (November 8, 1857 – March 24, 1940) was an American botanist, horticulturalist, and landscape architect closely associated with San Diego, California.

[7] In 1900, Sessions travelled to Baja California to find a palm tree not native to San Diego to be planted at the park.

[7] Together with Alfred D. Robinson, she co-founded the San Diego Floral Association in 1907; it is now the oldest garden club in Southern California.

[10] Sessions collaborated with architect Hazel Wood Waterman on the garden design of a single-family home near Balboa Park built by San Diego socialite Alice Lee.

Sessions never married,[5] but maintained a close and lifelong friendship with Alice Eastwood and some people speculate that she may have been a member of the LGBTQ+ community.

Sessions' work with plant introduction, as well as her extensive writing on the subject, won her international recognition.

At the California Pacific International Exposition on September 22, 1935, the day was dedicated to Sessions, where she was named the "Mother of Balboa Park".

[15] In the San Diego area, the Kate Sessions Elementary school in Pacific Beach bears her name, as does Kate Sessions Memorial Park on Mount Soledad, located less than a mile from the school and constructed only a few years later.