Maggie May - Rod Stewart
Bed of Roses - The Statler Brothers
I was 17 when it was new, and I remember a lot of us thinking his jailbait songs were creepy.
This Girl Is A Woman Now.
I think that one’s about, uh, practicing for your first boning. 
How?
No confirmation of virginity being lost in the song. Sounds like the young guy has been around.
A dream…not a woman.
A woman can wonder about that and not be a virgin. Also, this thread is about the guy losing his virginity.
Mentioned in the OP that it’s not clear that it’s his first time.
Come on Eileen oh I swear (what he means)
Ah come on lets, take off everything
That pretty red dress, Eileen (tell him yes)
Ah come on lets, ah come on Eileen
That pretty red dress, Eileen (tell him yes)
…
Now you’re full grown
Now you have shown
Oh, Eileen
Are you asserting that “now you’re full grown” means that she complied and had sex? I don’t think so. Earlier in the song is:
You’re grown (so grown up)
So grown (so grown up) now I must say more than ever
And after:
Now you’re full grown
Now you have shown
Oh, Eileen
the singer is still singing about how turned on he is with her in that dress, in a way that implies his wishes have not been answered - he’s still talking about her in the dress and asking her to “come on.” The two times it’s mentioned that she’s now full grown seems to imply that she’s older and really filling out that dress.
Finish the song. 
For the first time for a woman, no song is more explicit than Rod Stewart’s Tonight’s the Night. Any more explicit, and it would have not been played on the radio back then.
Are you thinking of Imaginary Lover? That one was definitely about “practicing.”
David Bowie’s “Young Americans”:
They pulled in just behind the bridge
He lays her down, he frowns
“Gee my life’s a funny thing, am I still too young?”
He kissed her then and there
She took his ring, took his babies
It took him minutes, took her nowhere
Heaven knows, she’d have taken anything, but
All night
She wants the young American
Well, it’s a third-person narrator, so it may not technically fit your topic. But it certainly seems to describe the first time for both participants.
Cher, Gypsies, Tramps, and Thieves
Picked up a boy just south of Mobile,
Gave him a ride, filled him with a hot meal;
I was sixteen, he was twenty-one.
Rode with us to Memphis,
And Papa woulda shot him if he knew what he’d done…
Queen, “Fat Bottomed Girls”.
“I was just a skinny lad,
Never knew no good from bad,
But I knew love before I left my nursery.
Left alone with big fat Fanny,
She was such a naughty nanny,
Heap big woman, you made a bad boy out of me.”
“Am I still too young” suggests it’s his first time, but “she’d have taken anything” doesn’t certainly seem to describe her first time.
Not seeing it with this song, either. Also, to nitpick, these songs aren’t about a guy’s first time.
Blue Oyster Cult’s “Dominance and Submission”
I heard this song on the radio the other day and I thought of this thread. Actually, the first thing I thought was “Ew”.
Foreigner’s “It Feels Like the First Time”?
ok maybe not
“Like a Virgin”? :o
No, that’s a metaphor for big dicks.
Harry Chapin’s “I Wanna Learn a Love Song”
…It took another man’s wife in the real world life
To make this boy a man …
Does anyone else feel this dirty reading this thread?
Going back to the OP, gotta say, we need to get ourselves some writers and producers and come up with the actual song “The First Woman I Ever Boned”. And write it already in Rock, HipHop, and Country versions to shop it around. It’ll make someone’s career…
War is Hell on the Home Front Too is a particularly disgusting country song about some mope delivery boy getting deflowered by some slut whose husband is off fighting WWII. Don’t care to look up the singer, but the drool in his voice while singing it made it extra creepy.