WASHINGTON (AP) _ There was a time when women were not welcome in the military. So a young Massachusetts woman named Deborah Sampson disguised herself in men's clothing, told recruiters her name was Robert Shurtleff and enlisted in the army.

The year was 1782, her corps the Continental Army.

On the battlefield, she saw men shot and watched them die. She was honorably discharged the next year, becoming one of the first woman veterans in America. At the time, General Patterson said of her:

''The Revolution is full of miracles, and this young lady is one of them.''

Since Deborah Sampson's time, millions of women have worn the uniform of the United States and helped to defend their country; today, there are more than 1.15 million women veterans, about 4.1 percent of all living American veterans.

Now, they want their own war memorial.

''Before I die, I want to take my daughter to Washington to see the statue dedicated to American women veterans. I'm willing to work for that. How do we begin?'' a woman from Pennsylvania wrote.

''I hope this memorial will honor not only those who served but act as a milestone in the history of women veterans,'' said an Ohio woman who served in Vietnam. ''Many women have given their lives while in service and many others ... have been held as prisoners of war.''

''When you talk about veterans, most people think of men. They don't think about women,'' said June Willenz, executive director of the Women in Military Service for America Memorial Foundation, which is lobbying for the memorial. ''It's really something that's long overdue. Women wrote a very marvelous page in our history.''

But the Reagan administration does not share this enthusiasm, saying that ''only military memorials commemorating all members of the armed forces identified with a war or other significant event or branches of service of the armed forces should be authorized.'' Since the proposed memorial would honor only women, the National Park Service has signaled its opposition.

Regardless, the House of Representatives last Wednesday gave unanimous approval to the women's memorial, along with one honoring Korean veterans and another for 5,000 blacks who supported the cause of the American Revolution. The Park Service does not oppose the Korean and black memorials.

''They haven't treated the other requests this way,'' said Rep. Patricia Schroeder, D-Colo., a sponsor of the women veterans memorial. ''I can't think of another veterans memorial that's been turned down.''

As for the administration's argument that a memorial should honor all participants, she said, ''How do they explain the black memorial, how do they explain Iwo Jima? Some (memorials) are generic and some are not.''

But don't existing memorials also honor women who served in past wars? ''There may be some commemorating women but they don't look like women,'' Mrs. Schroeder said.

She and the four other women members of the House Armed Services Committee have written the National Capital Memorial Advisory Commission, urging it to endorse the women's memorial at a meeting Thursday.

''Women since the revolutionary days have heeded the call to serve their country in times of crisis and war, from Martha Washington to the eight women whose names are listed among the dead and missing at the Vietnam Memorial,'' Mrs. Schroeder wrote, along with Reps. Beverly Byron, D-Md., Marjorie Holt, R- Md., Lynn Martin, R-Ill., and Marilyn Lloyd, D-Tenn.

''We have grown up with slogans in the military of 'a few good men' never recognizing the few good women serving alongside,'' they wrote.

Today, more than 200,000 women serve in the armed forces.

Ms. Willenz said mainline veterans groups, such as the Veterans of Foreign Wars and the American Legion, support the proposal. Her committee, set up in September, plans to launch a campaign early next year to raise money for the women's memorial.

Their hope is that Washington, city of 106 monuments and memorials, may soon have one more.