How do you form the superlative in French?

Put a definite article (le, la, les) in front of plus or moins, then the adjective: le plus grand (the biggest), la plus petite (the smallest), les plus chers (the most expensive). The article agrees with the noun in gender and number, and the adjective agrees as well, so both pieces move together. For 'the least', swap plus for moins: le moins interessant (the least interesting). The same shape works for adverbs, but there the le is frozen: elle court le plus vite (she runs the fastest).

Why does the article appear twice in 'la ville la plus grande'?

Because grand is an adjective that normally follows the noun, and the superlative keeps that position. So you get the noun with its own article (la ville), then the superlative built on a second article (la plus grande): la ville la plus grande (the biggest city). Adjectives that go before the noun, like grand in some fixed senses or petit, don't repeat the article - le plus grand probleme (the biggest problem) has just one. The doubling is a feature of post-nominal adjectives, not a mistake.

What is the difference between le meilleur and le mieux?

Le meilleur is the superlative adjective ('the best'), used with nouns and agreeing with them: le meilleur restaurant (the best restaurant), la meilleure idee (the best idea), les meilleurs joueurs (the best players). Le mieux is the superlative adverb ('the best'), used with verbs and frozen in one form: c'est elle qui travaille le mieux (she's the one who works best), c'est lui qui chante le mieux (he sings the best). English uses 'best' for both; French splits them, and the split mirrors the meilleur / mieux comparative pair.

French Superlatives

A superlative says one thing tops the lot: the biggest, the least expensive, the best. French builds it by putting a definite article in front of the comparative marker plus or moins. The article agrees with the noun, the adjective agrees too, and for adjectives that follow the noun the article ends up written twice.

Formation: article + plus / moins + adjective

The core shape is le / la / les + plus / moins + adjective. Both the article and the adjective agree with the noun.

Noun gender / number	Superlative	English
masculine singular	le plus grand	the biggest
feminine singular	la plus grande	the biggest
masculine plural	les plus grands	the biggest
feminine plural	les plus grandes	the biggest

le plus grand (the biggest, masc sg)
la plus grande (the biggest, fem sg)
les plus grands (the biggest, masc pl)
les plus petites (the smallest, fem pl)

For "the least", swap plus for moins:

le moins cher (the least expensive)
la moins interessante (the least interesting)
les moins fatigues (the least tired)

The adjective still obeys every agreement rule from the adjective agreement page. The superlative adds an article on top; it doesn't change how the adjective itself agrees.

Position and the repeated article

This is the part that trips people up. Where the superlative sits depends on where the plain adjective sits, and that decides whether the article appears once or twice.

Adjectives that go before the noun (the BAGS set: bon, grand, petit, jeune, beau, and so on) keep the superlative before the noun, with one article:

le plus grand probleme (the biggest problem)
la plus petite chambre (the smallest room)
le plus beau jardin (the most beautiful garden)

Adjectives that go after the noun keep the superlative after the noun, and the definite article is repeated - once for the noun, once for the superlative:

la ville la plus grande (the biggest city)
le livre le plus interessant (the most interesting book)
les voitures les plus rapides (the fastest cars)
la question la moins importante (the least important question)

Pattern	Example	English
pre-nominal, one art	le plus grand probleme	the biggest problem
post-nominal, two arts	la ville la plus grande	the biggest city
post-nominal, two arts	le restaurant le plus cher	the most expensive restaurant

The doubled article is correct, not a typo. la ville la plus grande literally stacks "the city" and "the most big". You can sometimes hear la plus grande ville as well, pulling the adjective forward into the pre-nominal slot, but the repeated-article version is the safe textbook form for post-nominal adjectives.

"in" after a superlative is de, not dans

English says "the tallest in the class". French uses de, not dans:

le plus grand de la classe (the tallest in the class)
le meilleur restaurant de la ville (the best restaurant in town)
la plus belle plage du monde (the most beautiful beach in the world)
l'eleve le plus serieux de l'ecole (the most serious pupil in the school)

Think of it as "the tallest of the class" and you'll pick the right word every time. dans la classe would mean physically inside the room, which is not what a superlative is claiming.

The irregulars: meilleur, pire, mieux

The same three irregulars from the comparatives page carry straight into the superlative. They take an article but never take plus.

Base	Superlative	English
bon (adjective)	le meilleur	the best
mauvais (adj)	le pire	the worst
bien (adverb)	le mieux	the best (adverb)

le meilleur is an adjective and agrees with the noun in gender and number:

le meilleur restaurant (the best restaurant)
la meilleure idee (the best idea)
les meilleurs joueurs (the best players)
les meilleures notes (the best marks)

le pire is the worst. It has no separate feminine form - just le pire / la pire with the same word, and les pires in the plural:

le pire moment (the worst moment)
la pire erreur (the worst mistake)
les pires nouvelles (the worst news)

You can also say le plus mauvais in many contexts; le pire is slightly more formal and more emphatic.

le mieux is the superlative adverb and is invariable - one form, used with verbs:

c'est elle qui travaille le mieux (she's the one who works best)
c'est lui qui chante le mieux (he sings the best)
de tous les plats, c'est celui-ci que j'aime le mieux (of all the dishes, this is the one I like best)

meilleur vs mieux: the split that matters

English has one word, "best", for both. French splits it, and the split is the same one you met in the comparatives:

le meilleur = best adjective, sits with a noun, agrees: le meilleur film (the best film).
le mieux = best adverb, sits with a verb, never agrees: il joue le mieux (he plays the best).

If "best" describes a noun, you want meilleur. If "best" describes how someone does something (a verb), you want mieux. The bon / bien adjective-adverb pair behaves exactly like English good / well, and the superlatives inherit that same divide. The full comparative side of this is on the comparatives page.

Superlatives of adverbs

For adverbs, put le in front of plus or moins and the le is frozen - it never agrees, because there's no noun to agree with.

elle court le plus vite (she runs the fastest)
c'est lui qui vient le plus souvent (he's the one who comes most often)
parle le moins fort possible (speak as quietly as possible)
c'est cette route qu'on prend le plus rarement (that's the road we take least often)

The same invariable le is what you see in le mieux - an adverb superlative wears a frozen le whatever the subject.

Worked examples

Paris est la plus grande ville de France. (Paris is the biggest city in France.)
C'est le probleme le plus difficile de l'examen. (It's the most difficult problem in the exam.)
Elle a eu les meilleures notes de la classe. (She got the best marks in the class.)
C'est le pire film que j'aie jamais vu. (It's the worst film I've ever seen.)
De toute l'equipe, c'est lui qui joue le mieux. (Of the whole team, he's the one who plays best.)
Le TGV est le train le plus rapide du pays. (The TGV is the fastest train in the country.)
C'est elle qui repond le plus vite. (She's the one who answers the fastest.)

Common mistakes English speakers make

Using dans for "in" after a superlative: le plus grand dans la classe is wrong, it's le plus grand de la classe. Dropping the repeated article on post-nominal adjectives: la ville plus grande is wrong, it's la ville la plus grande. Saying le plus bon instead of le meilleur, or le plus bien instead of le mieux - the irregulars never take plus. And confusing meilleur with mieux: if it sits with a noun use le meilleur (le meilleur joueur), if it sits with a verb use le mieux (il joue le mieux). Finally, agreeing the le on an adverb superlative: it stays le even with a feminine subject - elle court le plus vite, not la plus vite.