Saint Mary's Square is a park and urban square across California Street from Old St. Mary's Cathedral in San Francisco's Chinatown, in the U.S. state of California.

Designed in 1957 by Robert Royston the square is a rooftop park located on the top level of a parking garage in San Francisco's Chinatown neighborhood. At the time, rooftop gardens were promoted in the city by real estate developers as a means to maximize build able areas, and were most often sited on two‐story, above‐ground parking structures. being one of the first below ground parking structures, the rooftop garden was put into the designs as an afterthought. the current existing park was redesigned from the historic park that occupied the space prior to the implementation of the underground parking.

Royston's design used a system of grids and multiple tones of concrete to draw attention from the geometry of the space, imposed on it by the virtue of being above a parking garage. by implementing low seat walls and the curved nature of the planting beds, he divided up the pedestrian spaces, generating a feeling of nature within the space. The park has access to the street via a wide concrete staircase on one end and an at-grade entrance at the other. An existing row of poplar trees was retained as backdrop for the park, and a sculpture of Sun Yat-Sen by local artist Benny Bufano provides a focal point for the space. The park also includes a playground and refreshment stand.

The park features several culturally significant implements to the surrounding area, being a central community hub for the Chinatown area.

A privately funded statue that was placed in 2017 after being approved by the Board of Supervisors. The memorial is controversial as the sculpture honors the comfort women who were women and girls forced into sexual slavery by the Imperial Japanese Army in occupied territories before and during World War II. The mayor of Osaka, Japan stated he would sever the sister-city relationship with San Francisco as "the relationship of trust has completely been destroyed".

The statue of Sun Yat-sen by Beniamino Bufano is a 14-foot statue made of red granite and stainless steel, stands in St. Mary's Square. It is inscribed: "Dr. Sun Yat Sen 1866-1925 Father of the Chinese Republic and First President Founder of the Kuo Min Tang Champion of Democracy Lover of mankind: Proponent of friendship and peace among the nations, based on equality, justice and goodwill".

A memorial plaque in dedication to the Americans of Chinese ancestry who gave their lives for America in World Wars I and II. Reads, "We Salute these Americans of Chinese Ancestry who gave their lives for America in World Wars I and II".

Names included on the memorial

Tom Kwong	Coom G. Lee	Don Tung Sing	Faye Lowe	William L. Y. Goo
Leo Sai	Chin T. Tom	Eddie Soo	Mo S. Jee	Hong S. Hoey
Bill Tom	Yuen Hop	Manuel K. Soo	Alvin Richard Wong	Yee Nee Jin
Donald Ginn Chong	Walter Tom Lum	Harry Chew	James Q. Fong	Gene F. Lay
Lincoln Mark	Tow Jer	William Chew	Lloyd Quon	Jerry M. Lum
Tung Ling Yee	Ging Gin	Richard W. Chin	Frank Wong	Rudolph Lym
Harry Wong	Benjamin Ralph Kimlau	Richard Chong	Sing Fa Ping	Jeong Wing Jeen
Daniel Lim	Samuel Choy Sin	Marshall K. Dong	Castro Yu Hing Owyang	Harry Wong
Clifford S. Low	Clinton J. Lok	Albert P. Fong	Robert W. Chin	Wesley Y. Chow
Hon Y. Lee	Choy Young	Gong B. Fong	Charles J. Chan	Fan Yee Wong
John Wing Yee	Douglas C. Foo	Lew B. Tong	William J. Quan	Jack Dai Sum Yim
Get G. Chung	Edward Dewey Quong	Wong F. Gin	Thomas Yoke Jow Lai	Lem Quock Hing
Harry Choy	Alwyn G. Wong	Lee Wong Gem	Sam Wong	Lew Hung Biew
Collin S. Chong	Tang Chu Don	Howard Lee	Taft Toy	Harry F. Lee
Alfred W. Chin	James Sing	Harold W. Young	Lee Tan	John J. Chan
Leslie Y. Gee	Yee Sing You	Hong Chew Lee	Hom Wing On	George Lew
Ed Sam Fong	Edward Yin Ong	Percy Louie	Curtis C. Wong	Bob Chan
Ah Fong	Cheng Kee	Yee Lem	Sho Ling	Yeung Yaun

A ginkgo biloba tree planted in March 2017, honors Chinatown activist Rose Pak.

St. Mary's Square includes the former location of the Kong Chow Temple.

• Media related to Saint Mary's Square, San Francisco at Wikimedia Commons