Does sex equal marriage? Are unmarried couples who have sex married in the eyes of God?

TL;DR:

Having sex does not equal marriage and does not make a couple married. However, having sex is a union and has serious ramifications outside of marriage.

The short answer to the question of whether sex equals marriage is "no." Having sex does not make a couple married in God's eyes. Marriage is much more than just having one sex partner for the rest of your life; marriage is a total union of two persons physically, legally, and materially. Having sex with your significant other does not make you married because marriage is more than sex. Marriage is the legally binding promise to give yourself wholly to another for the rest of your life. Sex before marriage is damaging because it separates sex from this promise. God, knowing the beauty and intimacy of sex, protects us from hurting ourselves when He tells us to reserve sex for marriage.

from the old testament

The Old Testament, especially Song of Solomon, celebrates sex within marriage as a beautiful expression of love, intimacy, and joy. It portrays marital intimacy as a good gift from God, meant to deepen the bond between a husband and wife (Song of Solomon 4:10–16; 7:6–12).
Proverbs 5:18–19 also highlights the joy and satisfaction found in faithful marital love.

from the new testament

The Bible has many passages warning against sexual immorality, with fornication (any sexual act outside of marriage) being included within this range of acts (Acts 15:20; 1 Corinthians 5:1; 6:13; Galatians 5:19; Ephesians 5:3; Colossians 3:5; 1 Thessalonians 4:3; Jude 1:7).
God created marriage as a covenant, and He is the one who binds the couple together (Matthew 19:6).
Sex is an act of the marriage covenant that binds a man and woman together in physical and spiritual intimacy, mirroring the legal binding of the couple (Genesis 2:24).
Sex is a way of giving yourself completely to another person, and the covenant of marriage provides the freedom and safety to give oneself wholly (Matthew 19:6).
The writer of Hebrews says about marriage and sex in marriage: "Let marriage be held in honor among all, and let the marriage bed be undefiled" (Hebrews 13:4).

implications for today

Marriage is a lifelong commitment to love, honor, and cherish one another before God and others, and sex is a gift meant to be enjoyed within this covenant. When we engage in sex outside of marriage, we misuse this gift and risk binding ourselves emotionally, physically, and spiritually to someone without the foundation of commitment that marriage provides. This can lead to emotional wounds, broken trust, and spiritual disconnection. We should take seriously the weight of sex and live for God’s glory by enjoying sex within the context of marriage, where it strengthens our bond with our spouse and reflects God’s pure and faithful love for His people.

Sex without marriage, even in a committed relationship, holds on to the option of walking away when one's needs are not being met, and this is not the covenantal love of marriage. This is love that keeps oneself first, rather than one's significant other. God's desire is for us to enjoy all the love and support of intimate, committed relationships, and therefore, He has given us the best way we can experience this on earth through marriage.

understand

Marriage is more than just a physical act; sex does not equal marriage.
While it doesn’t make a couple married, sex still binds two people together—physically and emotionally.
Marriage provides the stable foundation God intended for sex.

reflect

How does understanding that sex does not equal marriage, but that sex is something that binds two people help you understand the importance of following God’s intent for sex?
How can you ensure that you approach intimacy within the context of commitment, reflecting the covenant of marriage?
What are some personal boundaries you can establish to honor God’s intention for sex and relationships in your life?

engage

How does the cultural perception of sex and marriage differ from the biblical perspective, and how can we respond with the truth of God’s design and purposes?
What are the emotional and spiritual ramifications of engaging in sex outside of marriage?
How can the church better communicate the importance of reserving sex for marriage to help individuals understand its significance in a covenant relationship?