Crowe was nominated for outstanding male actor in a leading role for his portrayal of the schizophrenic, Nobel Prize-winning mathematician John Forbes Nash Jr. in "A Beautiful Mind." Spacek was nominated for outstanding female actor in a leading role for her work as a woman struggling to cope with the tragic loss of a child in "In the Bedroom."
The guild -- which calls its award the Actor -- uses the term "female actor" instead of the word "actress."
Both Crowe and Spacek recently won Golden Globe Awards for their performances.
Crowe -- who won the Oscar last year for "Gladiator" -- was named best actor by the Broadcast Film Critics Association for "A Beautiful Mind," and was nominated in the category by the American Film Institute.
Spacek -- who won the Oscar in 1980 for her performance as country singer Loretta Lynn in "Coal Miner's Daughter" -- has scooped up most of the best actress honors during the current awards season, and is widely seen as the front-runner for the Oscar. In addition to the Golden Globe, Spacek won best actress honors from the AFI, the New York Film Critics Circle, the Los Angeles Film Critics Association and the Broadcast Film Critics Association.
The other nominees for the SAG Actor award for male actor in a leading role are Kevin Kline ("Life as a House"), Sean Penn ("I Am Sam"), Denzel Washington ("Training Day") and Tom Wilkinson ("In the Bedroom").
It's Kline's first significant nomination of the awards season. Penn was nominated for best actor by the Broadcast Film Critics Association.
Washington's work as a rogue cop in "Training Day" has been well-received by critics and professional groups. He was named best actor by the AFI, the Los Angeles Film Critics Association and the Boston Film Critics Association (in a tie with Brian Cox of "L.I.E.") and was nominated for a Golden Globe.
Wilkinson was named best actor by the New York Film Critics Circle and was nominated in the category by the AFI.
The other nominees for the SAG Actor award for female actor in a leading role are Halle Berry ("Monster's Ball"), Jennifer Connelly ("A Beautiful Mind"), Judi Dench ("Iris") and Renée Zellweger ("Bridget Jones's Diary").
Berry was named best actress by the National Board of Review and was nominated for a Golden Globe and an AFI Award.
Connelly's turn as Alicia Nash, the impossibly patient and loving wife, is among the most honored performances of the awards season so far, but awards voters have been split on the question of whether hers was a leading or a supporting role. She won the AFI award for featured actress and the Golden Globe for supporting actress. Her SAG nomination for female actor in a leading role may lead academy voters to consider her for best actress, rather than supporting actress.
Dench -- one of the most respected actresses in Hollywood since her star turn in "Mrs. Brown" (1997) -- was nominated for a Golden Globe for her portrayal of writer Irish Murdoch in "Iris."
Zellweger was nominated for a Golden Globe and a Broadcast Film Critics Association Critics' Choice award for her starring role in the film adaptation of Helen Fielding's first "Bridget Jones" novel.
Kidman, who won a Golden Globe for her portrayal of a doomed dance hall girl in "Moulin Rouge," may yet contend for an Oscar -- but she will need to buck the historical trend to make it happen.
In five of the last seven years, the winner of SAG's female actor in a leading role statuette went on to win the best actress Oscar. Jodie Foster won the SAG award for "Nell" in 1994, when Jessica Lange won the Oscar for "Blue Sky," and Annette Bening won the SAG award in 1999 for "American Beauty," while Hilary Swank took the Oscar for "Boys Don't Cry."
In six of the last seven years, the winner of the SAG award for male actor in a leading role has gone on to win the best actor Oscar. The exception came last year, when SAG named Benicio del Toro best actor for "Traffic." Del Toro went on to win the supporting actor Oscar, as Crowe won best actor for "Gladiator."
The nominees for male actor in a supporting role are Jim Broadbent ("Iris"), Hayden Christensen ("Life as a House"), Ethan Hawke ("Training Day"), Ben Kingsley ("Sexy Beast") and Ian McKellen ("The Lord of the Rings: The Fellowship of the Ring").
Broadbent and Kingsley have been splitting up the lion's share of plaudits during the awards season so far, along with Steve Buscemi ("Ghost World"), who was not nominated for an Actor.
The nominees for female actor in a supporting role are Cate Blanchett ("Bandits"), Judi Dench ("The Shipping News"), Cameron Diaz ("Vanilla Sky"), Dakota Fanning ("I Am Sam") and Helen Mirren ("Gosford Park").
SAG also presents an ensemble award to the outstanding cast of a theatrical motion picture. The nominated casts are from "A Beautiful Mind," "Gosford Park," "In the Bedroom," "The Lord of the Rings: The Fellowship of the Ring" and "Moulin Rouge."
In the TV categories, the HBO crime family drama "The Sopranos" and the NBC White House drama "The West Wing" received four nominations each.
"The Sopranos" was nominated for male actor in a drama series (James Gandolfini), female actor in a drama series (Lorraine Bracco and Edie Falco) and ensemble in a drama series. "The West Wing" was nominated for male actor in a drama series (Martin Sheen), female actor in a drama series (Stockard Channing and Allison Janney) and ensemble in a drama series.
The other nominees for the male actor award are Richard Dreyfuss ("The Education of Max Bickford"), Dennis Franz ("NYPD Blue") and Peter Krause ("Six Feet Under"). The other nominees for female actor in a drama series are Tyne Daly ("Judging Amy") and Lauren Graham ("Gilmore Girls").
The other nominees for the drama ensemble award are "CSI: Crime Scene Investigation," "Law & Order" and "Six Feet Under."
The CBS comedy "Everybody Loves Raymond" dominated in the comedy series categories with four nominations. Ray Romano and Peter Boyle were nominated for outstanding male actor in a comedy series, Patricia Heaton was nominated for female actor, and the cast was nominated for outstanding ensemble.
HBO's "Sex and the City," NBC's "Frasier" and "Will & Grace" had three nominations each, including a comedy ensemble nomination for all three shows.
Sarah Jessica Parker and Kim Cattrall of "Sex and the City" were nominated for female actor in a comedy series. "Frasier" stars Kelsey Grammer and David Hyde Pierce were nominated for male actor in a comedy series. "Will & Grace" stars Megan Mullally and Sean Hayes were nominated for female actor and male actor in a comedy series.
The other nominee for female actor in a comedy series is Jennifer Aniston, for "Friends" -- which is also up for a comedy ensemble award.
Alan Alda ("Club Land"), Richard Dreyfuss ("The Day Reagan Was Shot"), James Franco ("James Dean"), Gregory Hines ("Bojangles") and Ben Kingsley ("Anne Frank") were nominated for outstanding male actor in a TV movie or miniseries.
Angela Bassett ("Ruby's Bucket of Blood"), Judy Davis ("Life With Judy Garland: Me and My Shadows"), Anjelica Huston ("The Mists of Avalon"), Sissy Spacek ("Midwives") and Emma Thompson ("Wit") were nominated for outstanding female actor in a TV movie or miniseries.
The eighth annual Screen Actors Guild Awards will be presented March 10 in Los Angeles, in ceremonies to be televised live on TNT.