Is there a language spoken in the world that is nearly always spoken with grammatical correctness by its native speakers?

Every language is spoken correctly by its native speakers. Language IS what its native speakers speak. On the other hand, the question may mean three different things. If the question means whether there are languages that are very unified and don't have dialects — which therefore means that there are not variants judged as "incorrect" — the answer is sure: small languages spoken in small areas don't have much variation. For instance Icelandic (which, however, is not as small a language as most endangered languages are) does not have variants that would be called dialects although there certainly is some variation. The other interpretation of this question is whether there are languages that have a very little difference between spoken and standardised variants. Russian has very little dialectical differences and also the difference between the spoken and written language is small, or at least many people favour the standard form in their daily speech. Karelian does not have a strictly unified written language. Therefore, a reporter can write an article with a suitable dialect and cite his interviewees in their dialect and it's all correct. The third option is whether there are languages that are spoken only in their standardised form. Well, there was at least one. The Roman elite spoke very standardised form of Latin called Latinitas which was considered the "pure Latin" (although worker class had their own variants). However, it was not appropriate to speak too purely; they thought that language needed some character which meant that the elite, too, was supposed to use some non-standard features in their speech sometimes. It is important to note that standard languages are artificial constructions that have been invented much later than the spoken variants. Some languages use a mixture of dialects on the base of their standard language (for example Finnish and Norwegian nynorsk). It's not more correct than the original dialects. Some languages use one dialect as their standard language (for example Italian and Japanese). That does not make the chosen dialect more correct. Some languages use even written form based on another language (for example Norwegian bokmål that has its roots in Danish, which actually could be classified just as another dialect). It does not make local variants less correct. Colloquial and standard languages are different registers. They are used in their own situations. None of them is more correct language. It is the situation that makes the language used correct.

Yes, there are somewhere between 6-7000 of them. In other words, every language in the world is spoken with grammatical correctness by its native speakers. For linguists, native speakers are what define the grammar of a language. Quite literally, the tried and tested way of linguists determining the "correct" grammar of a language involves presenting possible sentences to native speakers and asking them whether or not they find them grammatical. The only way to access what is "correct" in a language is make a comprehensive description of how that language is used. This is known as descriptive linguistics. Data from descriptive linguistics is often used to create prescriptive grammars. What you may mean is "is there a language where all native speakers adhere perfectly to to the prescriptive grammar?". In this case, no. There is a lot of variation between speakers in a given language, so to some extent, what they consider correct will vary. For example, to an American ear "the government is calling for caution" is fine, but this would seem incorrect to a British ear (to them, it should be "the government are calling for caution"). Beyond this sort of thing, even native speakers make mistakes all the time, especially in spoken speech. In fact, http://en.wikipedia.org/wiki/Speech_error is a very interesting source of data, because people make some kinds of errors but not others. For more information, see here: http://www.ling.upenn.edu/courses/ling001/prescription.html

Any programming language.

According to my mum (who was a Mandarin speaker), Mandarin is nearly always spoken with a high degree of grammatical correctness vis a vis the written form by native speakers.

Barring slips-of-tongues and other such phenomena, every language is.

“Ok, let me rephrase again. Is there a spoken language in this world that follows the rules of the written version of its language exactly or nearly exactly, and also that is spoken in this way (following the rules of its written version exactly or nearly exactly) by its native speakers?”The answer to your edited question is still no. The reason is that your line of thinking is based on a fundamentally flawed assumption about the relationship between spoken and written language. Consider this:Written language is always a representation of an underlying spoken language not the other way around, not ever. By its very nature it can never capture spoken language perfectly. Think about Derrida’s idea of the signifier and the signified: written language is the signifier, spoken language is the signified. The signifier can never completely capture that which it signifies, no matter how painstakingly one tries.What I am writing right now does not give any indication of my accent or intonation for example, you do not know if I have a Swedish accent, a British one, or an American one.We can get close using special transcription scripts such as IPA. This is an actual research problem for linguists, since they have to adapt different transcription parameters, and make either rough or fine transcriptions depending on what level of language they want to investigate.“The idea that grammatical rules only apply to written language is saddening, and not something I'm likely to adopt anytime soon. “If there were no rules to spoken language..”Nobody has suggested this, your interpretation of the answers already provided is wrong. The distinction between descriptive and prescriptive language is important to understand here. Some languages (mostly those that have written forms) follow some set of very clear prescriptive rules, but every language follows its own descriptive rules. The “errors” that speakers make are, as somebody pointed out, logical given these descriptive rules. We tend to makes some “mistakes”, but not others. This is how language evolves.“…society would slide out of control very quickly, I think.”Most advanced societies in the world do have written languages. This gives a huge advantage because information can be recorded, stored, and re-accessed by other individuals. Still, written language has only been around for about 5000 years. Spoken languages have existed for far longer than that. I’m sure that even the ancient Sumerians had their prescriptivists.Suggestion: Become a descriptivist for a day! Try it! By adapting a descriptive stance to language I believe that you are going to find language much more interesting and exciting. You will be able to fully appreciate its beauty and complexity, and reject the idea that there is ever a clear-cut answer to any question.Best of luck.

Taking your revised question “Is there a spoken language in this world that follows the rules of the written version of its language exactly or nearly exactly, and also that is spoken in this way (following the rules of its written version exactly or nearly exactly) by its native speakers?”If there is, it is a bad one. Speaking/listening and writing/reading are different experiences. Even when the writing is giving recording narrative speech, it carries text to represent things carried by tone, context, direction in speech. Speech inevitably contains hesitations, fading out, repetition. Whereas writing can be more precise. And, because of that, you can have much longer, more connected thoughts in a written sentence. The reader can take it at their own speed, but needs punctuation and grammar to help. Whereas speech can give the same sort of guidance by stress and emphasis. Speech can sort out confusion between different actors in the same sentence in ways that writing cannot.So I see your question as asking “Is there anybody who drives in the same way through a crowded town centre as they do on a freeway”. I hope not.In fact, even speech varies. It has what are called different registers. If people spoke in the same way in a causal social occasions as they do in, say, a lawcourt, they would be regarded as seriously wrong in one or the other.Both speech and writing have grammars, but they are different grammars.

Other answers have already explained the difference between prescriptivism and descriptivism, so I won’t bother with that. I would like to point out, however, that under descriptivism, there is such a thing as “correct grammar” and “incorrect grammar”. However, what the grammar rules are differs between dialects.Let’s take the sentence you gave as an example of “improper grammar”: I don’t got no argument with that. You say that you feel that if you were to say this, you would be speaking with improper grammar. Of course you feel that way, because in your dialect, it is ungrammatical. Your dialect probably doesn’t allow double negatives or the use of “got” alone to mean “have”. And that’s perfectly fine. Every dialect of every language has rules like that.However, in some other dialects, it’s perfectly fine to use double negatives for emphasis or even any time a sentence is negated, and it’s common and correct to use “got” alone to mean “have”. In some other languages, such as Spanish, double negatives are obligatory in many cases, and words change meaning all the time in all languages, so there’s no reason a dialect of English can’t have those rules.So descriptivists aren’t arguing that “grammatical rules only apply to written language”. They’re arguing that “nonstandard” dialectal speech still follows fixed grammar rules just like the dialect considered standard. If “nonstandard” speech really had no rules, then instead of the sentence above, you might hear this:Argument no that with got not do me.I used all the same words, except for switching the subject pronoun “I” with the object pronoun “me”. If there were truly no grammar rules in colloquial spoken language, then there would be no problem with that sentence in informal speech, and it would be just as “correct” as the one further up. However, this sentence clearly breaks several grammar rules that are present in the dialect in which the sentence you gave is allowed: In a declarative sentence, the subject goes before the verb, and the verb goes before the object. Subject pronouns like “I”, not object pronouns like “me”, must be used in the subject position (there may sometimes be exceptions to this, but not here). Adjectives go before the nouns or noun phrases they modify and prepositions go before their objects. The word “not” goes after the verb it negates. Auxiliary verbs like “do” go before the main verb. Prepositional phrases go after the object of the main verb. So, as other answers have stated, all languages are spoken with grammatical correctness by their native speakers, because all native speakers follow fixed grammar rules, even if those rules differ between dialects.

You’re making the standard error of any lay person (i.e. not trained in linguistics), which is to believe that because you speak one language you therefore understand the details of how and why and the many ways it works. Sadly this is not true, and the reason there is a branch of study known as linguistics which is vast, and to me, fascinating.You probably believe you speak English, and maybe even believe you speak Standard English or maybe Standard American English. The problem is, there is no such thing. Everyone who speaks English, speaks a dialect of it. Everyone. All those dialects have grammars with pretty strict rules… it’s just it’s not the same set of rules! The grammars nonetheless are self-consistent such that you cannot just put words in any order and have them be classed as a valid sentence in that dialect.Much of what is purported to be “Standard English Grammar” is in fact just a stylistic preference. It’s the difference between writing in a formal context or an informal one, and no more important than that. To a linguist, language is used for communication. Doing so successfully and accurately (with as little error in communication as possible) is all that’s required. And yes, that may mean that a particular dialect of English may not be intelligible to a speaker of another dialect of English, but is nonetheless grammatically correct.Lay people are usually horrified by all of this, because they’ve been through a schooling system that pretends there is “one true grammar”, and think that not having this may mean a descent into linguistic chaos. But linguistic chaos is not what has ensued despite thousands and probably tens of thousands of years of human language… humans are remarkably adept at meeting other humans that use a different dialect or language… and hammering out new rules or learning the other set of rules… or both! Such is why creoles and pidgins exist! And living languages… languages where significant numbers of people are learning them as their L1s are always changing and growing. Interestingly, the grammatical rules show patterns, so humans clearly like certain ways of expressing themselves… but there’s plenty of variety :-)