What it means
Dreaming about sex is a normal part of almost everyone's dream life, whether they're in a relationship or not. The scenes may involve your partner, a stranger, someone you like or someone you'd never imagine. The fact that the dream happens doesn't mean you want it in waking life.
Often these dreams are about intimacy in a broad sense: wanting closeness, wanting to be seen, wanting to connect with someone. Other times they reflect vitality, a body with energy to spare. And sometimes the person in the dream stands for a quality of theirs, like confidence or tenderness, that attracts you or that you'd like to take on.
There's no need for guilt, either. You don't choose what you dream, and any awkwardness it leaves usually passes quickly if you look at it with curiosity instead of judgment.
Common variations
Sex with your partner
It usually reflects closeness, desire, or a wish to reconnect if there's been little time for intimacy lately. If the dream is more intense than real life, maybe there's something you'd like to suggest or explore together.
Sex with a stranger
A faceless or nameless person usually stands for something new: something in you that's waking up, a curiosity, a wish for novelty. It's not about anyone in particular, nor about what you'd do awake.
Sex with someone unexpected
A friend, a coworker, a celebrity, or someone you're not even attracted to: few versions puzzle people more. It almost always speaks of admiration, a bond getting closer, or a quality of that person, not real desire.
Sex with someone of a gender you're not drawn to
Lots of people have erotic dreams that don't match their orientation, and it's normal. They don't change who you are or reveal a hidden desire: dreams mix people, feelings and scenes with enormous freedom.
Being interrupted or walked in on
Someone walking in, an audience, or not being able to finish tends to touch on embarrassment, a lack of privacy or the feeling that your needs don't get any room. Notice who showed up and where you were.
What psychology says
A study by Antonio Zadra, presented at the SLEEP 2007 meeting, went through more than 3,500 dreams that men and women recorded in diaries and found sexual content in about 8% of them, at similar rates for both groups. These dreams draw on waking interests and emotions, but very loosely: dreaming something isn't the same as wanting it.
In folklore
Some popular beliefs read these dreams as an omen of infidelity or of changes in a relationship, while others load them with guilt or sin. Those ideas tend to cause more anxiety than understanding. A sex dream is an ordinary human experience: it doesn't oblige you to anything and says nothing about your morals.
Frequently asked questions
Is a sex dream about someone else cheating?
No. A dream isn't a choice or an action. Dreaming about someone else is very common in happy relationships and usually speaks of admiration, curiosity or something that person represents, not a wish to cheat.
Does a same-sex dream say something about my orientation?
Not on its own. Dreams combine people and scenes very freely, and these dreams turn up in people of every orientation. You know your orientation from what you feel in waking life, not from a dream.
Dreams are personal: these readings invite you to reflect, they don't decide for you. They are not medical or psychological advice. If you have frequent nightmares or sleep badly, see a professional.