“Children of Men” (2006)
https://www.youtube.com/watch?v=2VT2apoX90o&ab_channel=RottenTomatoesClassicTrailers
In the year 2027, after eighteen years of total human infertility, war and global depression have pushed society to the brink of collapse as humanity faces extinction. The United Kingdom has become a police state in which immigrants (derogatorily referred to as “’fugees”) are arrested and either imprisoned or executed; still, as one of the few remaining nations with a functioning government, it is deluged by refugees fleeing chaos in their own countries.
There was also a Mary Shelly novel about a world with only one man left on it. Never read it, but I surmise he’d be exhausted saving the world one shagging at a time.