Summarize:

The easiest way to avoid an unwanted marriage proposal is to let your partner know where you stand in the relationship. Because people change over the course of relationships, it is important to have open and honest conversations with your partner regularly. If your feelings have changed or you find that you are not ready to get married, let them know how you feel. It is important that you talk with your partner about any misgivings that you may have about marrying them. If your attitudes have changed, you might say something like “I know that we said that we would get married someday, but I’m not sure I want that anymore.” If you are in a relationship with someone, letting them know how you feel may not be enough to deflect a proposal. You should also be asking your partner how they feel about marriage. You may find that they are more serious than you are, which is something that you should address. You should ask things like “where do you see this going?” or “do you want to get married someday?” If you and your partner are at odds about the direction your relationship is going, you may want to get some relationship counseling. A therapist who specializes in helping couples fix their relationships may be able to help you better understand your partner’s desire to get married and, conversely, your aversion to it. This may help you mend your differences and jump-start communication between you and your partner. If you have been unclear about where you stand in the relationship, your partner might give you an ultimatum. They may say that the two of you should get married or break up. If they give you an ultimatum you should decline and talk with them about why they offered it. You should avoid being coerced into any relationship, particularly marriage. Ideally, if you are honest and communicate your intentions with your partner, you should not have to face an ultimatum. If you and your partner are unable to resolve your differing opinions about marriage, the best solution may be to end the relationship. This may be difficult but moving on is likely the best option. Again, be sure that you are honest with your partner about why you are leaving the relationship.  It is unfair to your partner to continue in a relationship if you do not want to commit to them. Be sure you want to end the relationship. It is important that you are confident that leaving your partner is the best option for you.
Talk honestly with your partner. Ask questions. Get help. Avoid any ultimatums. Break up.