It's remembering the family members, friends and comrades who gave their lives to help protect our country.
This weekend, many on social media have been honoring the fallen by sharing patriotic scenes and other powerful images -- many from years past. It's a reminder that for each person's sacrifice, there are people who miss them and want to preserve their legacies online.
Here are some of their stories.
A bald eagle landed on a gravestone at Minneapolis's Fort Snelling National Cemetery early one morning in June 2011, and amateur photographer Frank Glick was there to capture it.
The eagle had perched on the grave of Army Sgt. Maurice Ruch, a World War II veteran who died of Parkinson's disease at age 86 in 2008. Friends helped Glick track down Ruch's widow, and he presented her with a print of the picture.
"I'd say the eagle had a very good eye when he landed on Maurie," Vivian Ruch told the Star-Tribune in 2011
A widow's watch
The poignant story of Marine widow Katherine Cathey continues to resonate on Twitter.
Cathey was pregnant in August 2005 when she learned that her husband, Marine 2nd Lt. James Jeffrey Cathey, had been killed in Iraq. She stayed beside his casket the night before his burial, playing his favorite music as Marines stood guard over the family.
Their son was born just before Christmas that year and named after his father.
Honoring a fallen comrade
Retired Army Sgt. Noah Galloway, who came in third place
on "Dancing with the Stars," used his Instagram account Monday to pay tribute to fallen comrades.
The disabled veteran, now a motivational speaker, posted portraits of two unnamed soldiers with the hashtag #neverforgotten.
Galloway lost part of his left arm and left leg during Operation Iraqi Freedom in 2005, but his determination made him a favorite of "DWTS" judges and fans.
An officer and his bride
The sacrifice implied by images of men and women in uniform is ever-present, even in times of joy.
A photo of Marine Corps Cpl. Caleb Earwood saying a prayer with his bride, Maggie, before their wedding Saturday caught fire after North Carolina wedding photographer Dwayne Schmidt
posted it to his Facebook page.
Although they are holding hands in the photo, the couple took pains not to look at each other until the ceremony.
"I have photographed a lot of weddings," Schmidt wrote. "This has to be one of the best things i have ever got to see much less photograph..Before the ceremony and before they saw each other Caleb said a prayer for their marriage and lives. AWESOME !!!"
Many people responded on Facebook with messages of support.
"I prefer seeing a man and women honoring God and each other before stepping into the unknown together than a photo of a group of half-dressed people, in a boat, on a lake, falling all over themselves, drunk and acting like idiots on Memorial Day Weekend," one commenter wrote.
But of course, every social media post can attract its critics.
"You do realize that Memorial Day is to honor the fallen soldiers and not a wedding, right? Given that, this is not the perfect image for Memorial Day," wrote one Facebook commenter.
That's why the new couple's family took to Facebook to say that they didn't ask "to be placed in the public eye and are not trying to be insensitive to those who have lost loved ones."