Phyllis Barbara Lambert CC GOQ FRAIC FRSC RCA (née Bronfman; born January 24, 1927) is a Canadian architect, philanthropist, and member of the Bronfman family.

Born in Montreal, Quebec, she studied at The Study, a premier independent school for girls, and was educated at the liberal arts Vassar College (A.B. in 1948). At the age of nine she was already committed to sculpture and her drawing skills were commented upon as remarkable early on in life. And at eleven she began exhibiting in annual juried exhibitions at the Royal Academy of Arts and the Société des Sculpteurs du Canada. While reading architecture history in New York she became engaged with the connections of art and architecture which would last a lifetime. Her family is of Jewish background.

On 17 May 1949, in Montreal, she married Jean Lambert, a French-German economic consultant and the only son of Adolphe Lambert of Elmhurst, Queens, New York. The couple divorced in 1954. After the divorce she decided to remain in Paris, living and working alone in a studio on her art and sculpting.

In 1951 Lambert's father Samuel Bronfman established Cemp Investments, a holding company for his four children, in which Phyllis was given a 22% ownership stake. It controlled the family's distilling empire, The Seagram Company Ltd., which over time controlled billions of dollars in liquor, real estate, oil and gas, and chemical companies.

While Lambert was living in Paris, the Seagram Company Ltd was planning a new headquarters in New York City under her father's instructions. During her time in Paris, she had come into contact with the newest artistic and architectural movements of the time. She was vehemently against the building that had already been designed for the plot by Pereira and Luckman Architects. In an eight-page letter to her father (dated June 28, 1954), the 27-year-old Phyllis managed to convince him to re-think the initial project. She was given the mandate to find a suitable alternative and after an extended research lasting six weeks Mies van der Rohe was brought forward as the new candidate. He received the project and became her mentor supporting her in her wish to become an architect. From 1954 to 1958, she was immersed in the process of designing and building the Seagram Building on Park Avenue in New York City. Though she enrolled at the Yale School of Architecture in 1958, she then changed to the Illinois Institute of Technology, which she felt better suited to what she wanted to learn.

Lambert later became the consultant to the Seagram Building, entrusted with its maintenance including the supervision and the curation of all exhibitions and collections, until 2000.

After she obtained her master's degree in 1963, her family commissioned her to design an arts centre in Montreal to be known as the Saidye Bronfman Centre, in honor of her mother. Lambert designed a ‘Miesian Structure’.

After the demolition of the Van Horne Mansion on Sherbrooke Street in 1973, 23 citizen groups formed Sauvons Montréal. Lambert became one of the advocates in the efforts to revitalize the struggling Shaughnessy Village district.