Is there a specific supplication (du'a) for marriage?

There is no specific supplication in Islamic law for someone who wishes to marry, but supplication is beneficial in all circumstances. As for the supplication for the married person when congratulating them, it is: "May Allah bless you, and may He bless upon you, and may He unite you both in good." And the supplication that the married man says when his wife is brought to him is: "O Allah, I ask You for her goodness and the goodness of what You have instilled in her nature, and I seek refuge in You from her evil and the evil of what You have instilled in her nature."