If you can produce one French subjunctive trigger fluently, make it il faut que. It is by a wide margin the most common subjunctive construction in spoken French — used dozens of times a day by every native speaker to say "I have to," "you need to," "we must," "he should." Every other subjunctive trigger feels like a piece of advanced grammar; il faut que is conversational glue. The phrase il faut que j'y aille — "I have to go" — is so frequent that it functions almost as a single lexical chunk, dropped into countless conversations as a way to leave politely.
This page covers the meaning and tenses of falloir, the il faut que + subjunctive construction with all its tense matches, the parallel impersonal il faut + infinitive, and the moments when one is right and the other is wrong.
The verb falloir: impersonal, defective, irreplaceable
Falloir is an unusual verb in three ways. It is impersonal — the subject is always il, and that il refers to no one (the same dummy subject as in il pleut, "it's raining"). It is defective — it has no first-, second-, or plural-person forms, no gerund, no imperative. And it is the standard French way to express necessity: there is no everyday verb meaning "must" in French. Devoir exists, and we will compare them, but falloir is the more frequent and more emphatic of the two.
The full set of forms you actually use:
| Tense | Form | Translation |
|---|---|---|
| présent | il faut | it's necessary / one must / one has to |
| imparfait | il fallait | it was necessary / one had to |
| passé composé | il a fallu | it was necessary (one specific time) |
| plus-que-parfait | il avait fallu | it had been necessary |
| futur simple | il faudra | it will be necessary |
| conditionnel | il faudrait | it would be necessary / should |
| subjonctif | qu'il faille | that it be necessary |
Note the irregular stems: fau- in the present, fall- in the imperfect and participle, faud- in the futur and conditionnel. All seven forms above are common in everyday French — even the conditional il faudrait is one of the most frequent ways to soften advice.
Il faut que + subjonctif: the canonical productive construction
When falloir takes a que-clause with a specific subject, the verb in that que-clause goes into the subjunctive. This is the canonical productive use of the French subjunctive — the construction that makes the subjunctive a living part of the spoken language rather than a museum piece.
Il faut que j'y aille.
I have to go. (Said when leaving a conversation, a party, the office. Possibly the most common subjunctive sentence in French.)
Il faut que tu manges quelque chose, tu n'as rien pris depuis ce matin.
You have to eat something — you haven't had anything since this morning.
Il faut qu'on parte maintenant si on veut éviter les embouteillages.
We have to leave now if we want to avoid traffic.
Il faut que vous fassiez attention à cette marche, elle est plus haute qu'elle n'en a l'air.
You need to watch out for this step — it's higher than it looks.
Il faut qu'il rende sa chambre avant midi, sinon il devra payer une nuit de plus.
He has to check out of his room before noon, otherwise he'll have to pay for another night.
The structure is rigid: il faut + que + subject + verb in subjunctive. There is no il faut tu manges (no que) and no il faut que tu manges with manges in the indicative — the subjunctive manges and the indicative manges happen to be identical for -er verbs in tu, but the verb is grammatically subjunctive. The match becomes visible with irregular verbs: il faut que j'aille (subjunctive) — never il faut que je vais (indicative, ungrammatical here).
Tense matching: the matrix tense determines the subjunctive tense
A useful pattern for B1 learners: the tense of falloir in the matrix clause does not change the rule (the que-clause is always subjunctive), but it does change which subjunctive form (présent or passé) shows up.
| Matrix tense | Example | Translation |
|---|---|---|
| il faut (présent) | Il faut que tu partes maintenant. | You have to leave now. |
| il fallait (imparfait) | Il fallait que tu partes plus tôt. | You should have left earlier. / You needed to leave earlier. |
| il a fallu (PC) | Il a fallu qu'on parte avant la fin. | We had to leave before the end. (One specific occasion.) |
| il faudra (futur) | Il faudra qu'il vienne demain. | He'll have to come tomorrow. |
| il faudrait (cond.) | Il faudrait que tu réfléchisses avant de répondre. | You should think before answering. |
Il fallait que je sois à Paris à 8h, donc je suis parti à 5h du matin.
I had to be in Paris by 8, so I left at 5 in the morning.
Il faudra que tu m'envoies les documents avant la réunion.
You'll need to send me the documents before the meeting.
Il faudrait qu'on se voie un de ces jours, ça fait trop longtemps.
We should get together one of these days — it's been too long.
The il faudrait que construction is especially worth practicing: it is the conversational French equivalent of "you should," "we should," "it would be a good idea to" — softer than il faut que, and the natural way to make a suggestion to a friend or coworker.
When the action is in the past or completed: il faut que + subjonctif passé
If the que-clause action needs to be completed before some moment, you use the subjonctif passé.
Il faut que tu sois rentré avant minuit.
You have to be home by midnight. (Completion required by a future deadline.)
Il faudra que vous ayez fini ce projet avant vendredi.
You'll need to have finished this project before Friday.
Il fallait que j'aie déjà signé le contrat pour pouvoir commencer.
I needed to have already signed the contract in order to start.
This is the standard way French expresses a future-perfect-style obligation. See Subjonctif Passé: Formation and Use for the full logic.
Il faut + infinitif: the impersonal alternative
Not every necessity has a specific subject. When the necessity is general — "one must," "people have to," "you in general should" — French uses il faut + infinitive without que.
Il faut manger pour vivre.
One must eat to live.
Il faut acheter du pain avant de rentrer.
We need to buy bread before going home. (Speaker including themselves in a generic 'someone needs to'.)
Pour réussir cet exercice, il faut comprendre la grammaire.
To succeed at this exercise, one has to understand the grammar.
Il faut être patient avec lui.
You have to be patient with him.
The two constructions are not interchangeable — they answer different questions:
- Il faut + infinitif answers "what is the rule / general necessity?" — no specific person.
- Il faut que + subjonctif answers "what does this specific person have to do?" — a particular subject.
| Construction | Subject? | Example | Translation |
|---|---|---|---|
| il faut + inf. | generic / unspecified | Il faut partir. | One must leave. / It's necessary to leave. |
| il faut que + subj. | specific | Il faut que je parte. | I have to leave. |
| il faut + inf. | generic | Il faut faire attention. | One must be careful. |
| il faut que + subj. | specific | Il faut que tu fasses attention. | You have to be careful. |
Il faut prendre rendez-vous à l'avance.
You have to make an appointment in advance. (General rule for anyone going to this place.)
Il faut que je prenne rendez-vous à l'avance.
I have to make an appointment in advance. (My specific situation right now.)
In casual spoken French, the il faut + inf. construction often replaces il faut que je + subj. when the speaker is talking about themselves and the context makes the subject obvious — a small simplification that's perfectly normal in conversation:
Bon, il faut y aller, je suis en retard.
OK, I have to go, I'm running late. (informal — clearly the speaker, no que-clause needed)
But the il faut que version is always available and always grammatically clearer:
Il faut que j'y aille, je suis en retard.
I have to go, I'm running late.
Il faut que vs. devoir: two ways to say "must"
French has two everyday ways to express obligation, and English speakers often struggle to choose. Here is the distinction in practical terms:
| Construction | Register | Strength | Example |
|---|---|---|---|
| il faut que tu partes | neutral / conversational | strong, often urgent | You have to leave. |
| tu dois partir | neutral, slightly formal | obligation, sometimes moral | You must leave / are supposed to leave. |
| il faudrait que tu partes | softened, polite | suggestion / mild obligation | You should leave. |
| tu devrais partir | softened, polite | advice | You should leave. |
In native usage, il faut que is the more conversational, more insistent of the two. Devoir is more flexible: it can mean obligation (tu dois faire tes devoirs), supposition (il doit être malade — "he must be ill"), or scheduled future (je dois voir le médecin demain — "I'm supposed to see the doctor tomorrow"). Falloir covers only obligation, but does so with greater frequency and force.
Il faut que tu lui dises la vérité — c'est la seule solution.
You have to tell him the truth — it's the only solution. (Strong, urgent, conversational.)
Tu dois lui dire la vérité.
You must tell him the truth. (More moralistic, slightly more distant.)
Il faudrait que tu lui dises la vérité.
You should tell him the truth. (Softened — advice, not an order.)
Il faut que: irregular verbs to drill
The most common subjunctive irregulars after il faut que are exactly the most common irregular verbs in French. Memorize the je / tu forms of these and you have most of conversational French covered:
| Verb | il faut que je / tu | il faut qu'il | il faut que nous / vous | il faut qu'ils |
|---|---|---|---|---|
| aller | j'aille / tu ailles | aille | allions / alliez | aillent |
| être | je sois / tu sois | soit | soyons / soyez | soient |
| avoir | j'aie / tu aies | ait | ayons / ayez | aient |
| faire | je fasse / tu fasses | fasse | fassions / fassiez | fassent |
| pouvoir | je puisse / tu puisses | puisse | puissions / puissiez | puissent |
| savoir | je sache / tu saches | sache | sachions / sachiez | sachent |
| vouloir | je veuille / tu veuilles | veuille | voulions / vouliez | veuillent |
| venir | je vienne / tu viennes | vienne | venions / veniez | viennent |
| prendre | je prenne / tu prennes | prenne | prenions / preniez | prennent |
Il faut que je sache la vérité avant de prendre une décision.
I need to know the truth before making a decision.
Il faut qu'on fasse les courses ce soir, le frigo est vide.
We need to do the shopping tonight — the fridge is empty.
Il faut que vous puissiez me joindre à tout moment.
You need to be able to reach me at any time.
Common Mistakes
Mistake 1: Using the indicative after il faut que.
❌ Il faut que je vais à la pharmacie.
Wrong: 'vais' is indicative. After 'il faut que' the verb must be in the subjunctive: aille.
✅ Il faut que j'aille à la pharmacie.
I have to go to the pharmacy.
This is the single most common subjunctive mistake English speakers make. Aller is one of the most frequent verbs and its indicative vais / vas / va is so reflexive that learners say it before the subjunctive aille / ailles / aille can come to mind. Drill this one until il faut que j'aille feels automatic.
Mistake 2: Dropping que in il faut que.
❌ Il faut tu partes maintenant.
Wrong: there is no 'il faut + subject + subjunctive' construction. Either use 'il faut que' with a subject, or 'il faut + infinitif' with no subject.
✅ Il faut que tu partes maintenant.
You have to leave now.
✅ Il faut partir maintenant.
It's necessary to leave now.
Mistake 3: Using il faut + infinitif when the subject is specific.
❌ Il faut moi aller à la banque.
Wrong: 'moi aller' is not a French construction. Use 'il faut que j'aille' for a specific subject.
✅ Il faut que j'aille à la banque.
I have to go to the bank.
Mistake 4: Trying to translate "must have done" with il faut + passé composé.
❌ Il faut que tu es parti avant 8h.
Wrong: 'es parti' is indicative passé composé. The subjonctif passé is needed: 'sois parti'.
✅ Il faut que tu sois parti avant 8h.
You have to be gone by 8.
Mistake 5: Misreading il faut as a polite suggestion.
❌ Il faut que tu viennes au restaurant ce soir, ça serait sympa !
Possibly too forceful — 'il faut que' is a strong obligation, not a casual invitation. To suggest, use 'il faudrait' or 'tu pourrais venir'.
✅ Il faudrait que tu viennes au restaurant ce soir, ça serait sympa !
You should come to the restaurant tonight, it'd be nice!
In invitations between friends, il faut que tu viennes can sound demanding rather than friendly. Use the conditional il faudrait — or shift to ça serait sympa que tu viennes — for a softer register.
Key takeaways
- Il faut que
- subjunctive is the most common productive subjunctive construction in French. Master it before any other trigger.
- The matrix can be in any tense (il faut, il fallait, il a fallu, il faudra, il faudrait) — the que-clause stays in the subjunctive.
- Il faut que
- subjonctif passé (= aies / sois
- past participle) marks a deadline by which the action must be completed.
- subjonctif passé (= aies / sois
- Il faut + infinitif is the impersonal alternative — used when there is no specific subject.
- Il faut que j'y aille — "I have to go" — is the highest-frequency subjunctive sentence in spoken French. Make it automatic.
- Falloir and devoir both express obligation, but falloir
- subjunctive is more conversational and often more forceful; devoir
- infinitive is more flexible (also covers supposition and scheduled events).
- subjunctive is more conversational and often more forceful; devoir
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