I'm assuming it to be a relatively standard sized lie ("my girlfriend left me last week" would be about the upper limit). IN which case, yeah, but only really if it's a one-night stand with someone you don't particularly know/don't know at all. Lying to get in bed with a friend is for some reason worse to me than lying to get in bed with a stranger.
Though, if your lie is something like "I come from a war-torn village in Africa whose unique customs include interesting and innovative sexual positions. Our entire village was wiped out by war, and I am the only survivor. Won't you help me keep our traditions alive?", no, it's never okay because that's basically the Nigerian Price scam.
Though, if your lie is something like "I come from a war-torn village in Africa whose unique customs include interesting and innovative sexual positions. Our entire village was wiped out by war, and I am the only survivor. Won't you help me keep our traditions alive?", no, it's never okay because that's basically the Nigerian Price scam.