Wat is jouw naam?

Because this is a direct question.

In Dutch, when a question starts with a question word like wat, the finite verb usually comes right after it:

• Wat is jouw naam?
• Waar woon je?
• Hoe heet hij?

So the pattern is often:

question word + verb + subject/complement

The order wat jouw naam is can appear inside a longer sentence, but not usually as a normal standalone question. For example:

• Ik weet niet wat jouw naam is.
  = I don't know what your name is.

Jouw means your.

It is the stressed/emphatic form of the possessive. Dutch often has:

• je = unstressed your
• jouw = stressed your

So:

• Wat is je naam? = neutral, very common
• Wat is jouw naam? = puts a bit more emphasis on your

That emphasis can be useful if there is contrast, for example:

• Ik weet zijn naam, maar wat is jouw naam?
  = I know his name, but what is your name?

It is correct and understandable, but it is not always the most common everyday phrasing.

Very often, Dutch speakers say:

• Hoe heet je? = literally What are you called?, meaning What’s your name?

Also common:

• Wat is je naam?

So the three forms are all possible, but they feel slightly different:

• Hoe heet je? — very common and natural in speech
• Wat is je naam? — normal and straightforward
• Wat is jouw naam? — correct, but with extra emphasis on your

Because these are two different sentence patterns for asking the same thing.

• Wat is jouw naam? literally asks: What is your name?
• Hoe heet je? literally asks: How are you called?

English strongly prefers What is your name?
Dutch often prefers Hoe heet je?

So wat is not wrong at all here; it just belongs to a different way of asking the question.

They all can mean your, but they differ in formality and emphasis.

• je — informal, unstressed, very common
• jouw — informal, stressed/emphatic
• uw — formal, or used when speaking politely to someone

Examples:

• Wat is je naam? — informal, neutral
• Wat is jouw naam? — informal, with emphasis
• Wat is uw naam? — formal/polite

If you are talking to a friend, je or jouw is normal.
If you are talking to a customer, older stranger, or in a formal setting, uw may be more appropriate.

Because Dutch, like English, normally does not use an article before a noun when it already has a possessive word like your.

Compare:

• de naam = the name
• jouw naam = your name

You do not say:

• jouw de naam

That would be incorrect. The possessive already determines the noun.

A rough English-friendly guide would be:

• Wat ≈ vaht
• is ≈ iss
• jouw ≈ yow
• naam ≈ nahm

A few notes:

• Dutch j sounds like English y
• Dutch aa is a long vowel, so naam has a long a
• Dutch w is not exactly the English w; it is often closer to something between English w and v

So the whole sentence sounds roughly like:

vaht iss yow nahm

That is only an approximation, but it is a useful start.

You can use it normally, and people will understand you perfectly. But compared with je, it often feels a bit more deliberate or emphasized.

So in everyday casual Dutch, many speakers would more naturally say:

• Wat is je naam?

Using jouw is especially natural when:

• you want contrast
• you want to stress your
• you are being extra clear

So jouw is not wrong at all — it just has a little more weight than je.