THE NATIONAL GALLERY of Art features a seven-film series of artist bio- graphies, starting Saturday at 2:30, with Alexander Korda's Rembrandt (1936), starring Charles Laughton. "Rembrandt" is repeated Sunday at 6. Next Saturday (October 17, 1:30), Jose' Ferrer plays Henri de Toulouse-Lautrec in John Huston's 1952 Moulin Rouge. On the same bill, George Sanders plays a character based on Paul Gauguin in Albert Lewin's 1942 The Moon and Sixpence. Vincente Minnelli's 1956 Lust for Life (with Kirk Douglas as Vincent van Gogh) plays Saturday October 24 at 2:30 and Sunday October 25 at 6. The remaining three films are Peter Watkins' 1976 Edvard Munch, November 1 at 6; Ken Russell's 1968 Dante's Inferno (actually about pre- Raphaelite painter Dante Gabriel Rossetti), November 7 at 2:30; and Georgi Shengelaya's 1971 Pirosmani, about Georgian artist Nikolai Pirosmanishvili (November 8 at 6). Admission for these films, at the Gallery's East Building auditorium, is free.

I've Heard the Mermaids Singing, a wry and quietly delightful movie by Canadian Patricia Rozema, opens next Friday (October 16). It's the story of a mousy girl waiting in the wings for just a little success. The Key Theater will sneak preview "Mermaids" this Sunday night at 7:20. Admission is $5 for those without prior invitation.

The American Film Institute continues its Yugoslavian film series. Friday at 6:30, it's Misa Radivojevic's The Promising Young Man (1981); on Monday at 8:30, Srdan Karanovic's Caught in the Throat (1985); Wednesday at 6:30, Dejan Sorak's The Small Train Robbery; and next Friday at 6:30, Boro Draskovic's Life is Beautiful. Admission is $3.50 members and $4.50 nonmembers. Call 785-4600.

The Potpourri of Free: Friday at 8, and Saturday at 1 p.m., the Hirshhorn Museum will show Robert Wilson and CIVIL warS, Howard Brookner's portrait of the visual artist who also made "Einstein on the Beach." In association with the Smithsonian's "Generations" exhibition, a series of documentary shorts about children, parenting and child-raising, Sunday 10:30 to 5, at the lecture hall of the Smithsonian's S. Dillon Ripley Center (1100 Jefferson Dr. SW). For Hirshhorn and Ripley activities, call 357-2700 . . . In conjunction with Washington's third Latin American Book Fair (See Weekend's Best on page 3), eight films on Saturday and Sunday at the University of the District of Columbia's auditorium (Van Ness campus). Saturday at noon, Bruno Barreto's Gabriela (in Room AO3, Building 41), then Hector Olivera's The Dead Man (in Room AO3, Building 41) at 2, Euzhan Palcy's Sugar Cane Alley at 4, and Fernando E. Solanas' Tangos, The Exile of Gardel at 6:45. Sunday at noon, Leopoldo Pinzon's Pisingana, followed by Hector Babenco's Kiss of the Spider Woman at 1:45, Suzanna Amaral's The Hour of the Star at 4, and Francisco Lombardi's The City and the Dogs at 6:30. Call 282-7538 . . . At the Library of Congress' Mary Pickford Theater, Jan Troell's The New Land (Tuesday at 7) and Joan Micklin Silver's Hester Street (Thursday, 7:30). Call 287-5677 . . . At the National Archives theater, two combat documentaries by Norman Hatch -- With the Marines at Tarawa (1944) and To The Shores of Iwo Jima (1945). David Hoffman will introduce his 1984 documentary Second Home, about military life on Lebanon-bound aircraft carrier John F. Kennedy, Tuesday at 3. The film's repeated next Friday (October 16) at noon. Call 523-3000 . . . Finally, Como Era Gostoso O Meu Frances will show Friday at 6 and 9, at the Brazilian-American Cultural Institute, 4103 Connecticut Ave. NW; admission $5. Translated, the title of this comedy (in French and Tupi with subtitles) is "How Tasty Was My Little Frenchman."