Isn't belief in God just wishful thinking?

Wishing does not make a thing true or false. The honest question is whether the evidence points toward God, and features like the existence and order of the universe, and our sense of real morality, are difficult to explain without him. Faith here is a reasoned trust, not a fantasy.

Can I ask God to show me he is real?

Yes. The Bible invites honest seeking and promises that those who search for God with their whole heart will find him. Many people find God becomes most real not at the end of an argument but in honestly asking him to make himself known.

Is it true?

How do we know God is real?

Q: How do we know God is real?

We cannot test God in a lab, but real clues point to him: that anything exists at all, that the universe is ordered and intelligible, that right and wrong feel genuinely real, and that people everywhere reach toward the transcendent (Romans 1:20). Together they make belief reasonable, and Christians say God showed himself most clearly in Jesus.

The short answer

We cannot put God in a test tube, but there are real reasons to take his existence seriously: that anything exists at all, that the universe is finely ordered and intelligible, that we cannot shake a sense of genuine right and wrong, and that people across all cultures reach toward something beyond themselves. None of these prove God like a math problem, but together they make belief reasonable rather than blind, and Christians add that God has shown himself most clearly in Jesus.

The question deserves more than a slogan. Belief in God is not meant to be belief against the evidence. Many people find that the deepest features of reality point beyond it: the sheer fact that there is something rather than nothing, and that the cosmos is ordered enough for us to understand it at all.

“For the invisible things of him from the creation of the world are clearly seen, being understood by the things that are made, even his eternal power and Godhead.”
Romans 1:20

The clues we live by

We treat love, justice, and human dignity as truly real, not as mere chemistry we could shrug off. That conviction is hard to explain if we are only atoms, and it fits well if we were made by a good God. Our restless longing for meaning points the same direction, as if we were built for someone we have not yet met.

“The heavens declare the glory of God; and the firmament sheweth his handywork.”
Psalm 19:1

The Bible does not ask you to fake certainty. It invites honest seeking and makes a bold promise to those who really look.

It comes back to Jesus

Christians believe the clearest window onto God is not an argument but a person. In Jesus, the invisible God stepped into history where we could see him, and he said that whoever had seen him had seen the Father. If you want to know whether God is real, start by looking honestly at Jesus and asking him to show you.

Keep exploring, no pressure

Talk it through: ask someone here to pray with you, no explaining required.
See the whole picture: the Gospel, explained simply.
Curious where to start? A gentle first step toward Jesus.
Related question: Is there proof that God exists?
Related question: Is faith reasonable?