There is no Class Z felony in Illinois. The label doesn’t appear anywhere in the Illinois Criminal Code, has never been proposed in the General Assembly, and isn’t used by any Illinois court. Illinois sorts every felony into one of six classes: Class M, Class X, and Classes 1, 2, 3, and 4. If you saw “Class Z felony” referenced online or heard it in conversation, it was either a mistake or an invented term, possibly borrowed from a different state’s system or confused with the alphabetical schemes some other jurisdictions use.
Here is what Illinois actually uses, and what each class means in practice.
The Six Felony Classes Illinois Actually Uses
Every felony prosecuted in Illinois falls into one of these categories, listed from most to least severe:
- Class M is reserved for first-degree murder. Nothing else goes here.
- Class X covers the most serious non-murder felonies: armed robbery, home invasion, predatory criminal sexual assault, attempted first-degree murder.
- Class 1 includes second-degree murder, aggravated robbery, and vehicular hijacking.
- Class 2 covers burglary, arson, robbery, and kidnapping.
- Class 3 includes aggravated battery, unlawful use of a weapon, and forgery.
- Class 4 is the lowest felony tier and covers offenses like domestic battery, obstruction of justice, and theft under $300.
When the Illinois legislature decides to criminalize new conduct, it assigns the offense to one of these existing classes. The system has no empty slot that a “Class Z” would occupy, and no proposal is pending to add one.
Sentencing Ranges for Each Class
Each class carries a base prison range the judge works within, plus a longer extended-term range available when specific aggravating factors apply.
Class M (First-Degree Murder)
Minimum 20 years. Maximum natural life.
Class X
Six to 30 years in prison under the base range, or 30 to 60 years under an extended term. Class X is the only non-murder felony class where probation is categorically off the table — the statute flatly prohibits it.1Illinois General Assembly. 730 ILCS 5/5-4.5-25 – Class X Felonies; Sentence A Class X conviction means prison, which is one reason prosecutors sometimes charge at the Class X level to create leverage for a plea to something lower.
Class 1
Four to 15 years base, 15 to 30 years extended term.2Illinois General Assembly. 730 ILCS 5/5-4.5-30 – Class 1 Felonies; Sentence Second-degree murder is the exception within the class, carrying a 4 to 20-year range.
Class 2
Three to 7 years base, 7 to 14 years extended term. A Class 2 conviction also carries 2 years of mandatory supervised release after prison.3Illinois General Assembly. 730 ILCS 5/5-4.5-35 – Class 2 Felonies; Sentence
Class 3
Two to 5 years base, 5 to 10 years extended term.4Illinois General Assembly. 730 ILCS 5/5-4.5-40 – Class 3 Felonies; Sentence
Class 4
One to 3 years base, 3 to 6 years extended term.5FindLaw. Illinois Code 730 ILCS 5/5-4.5-45 – Class 4 Felonies; Sentence This is the class most likely to result in probation rather than prison, especially for defendants with no prior record.
How Extended-Term Sentencing Works
An extended term roughly doubles the ceiling of the base range. A Class X ceiling moves from 30 to 60 years, a Class 1 ceiling from 15 to 30, and so on down the ladder. A judge can only impose an extended term when at least one aggravating factor listed in Section 5-5-3.2 of the Unified Code of Corrections applies. Those factors include things like the defendant holding a position of trust, the victim being particularly vulnerable, or the offense being motivated by hate.
There’s a procedural wrinkle worth knowing. If a defendant pleads guilty and the court plans to impose an extended-term sentence, the record has to show the defendant knew an extended term was on the table when they entered the plea. If that acknowledgment isn’t in the record, the defendant gets a chance to withdraw the plea.
When Probation Is Possible
Probation availability tracks the class. Class M and Class X convictions do not qualify for probation under Illinois law. Class 1 and Class 2 offenses may be eligible depending on the specific statute and the defendant’s history, though many Class 1 offenses carry presumptions against it. Class 3 and Class 4 convictions are the most likely to result in probation, particularly for first-time offenders, where judges often weigh mitigating factors like age, mental health, remorse, and willingness to make restitution.
None of this changes the conviction itself. A felony on the record is a felony on the record, with all the collateral consequences that follow, whether the sentence ends up being prison or probation.
Where the “Class Z” Idea Likely Comes From
Some states use longer alphabetical felony schemes. New York runs from Class A down through Class E. Other states extend further. None of them reach Z either, but someone unfamiliar with Illinois may have assumed the state uses a longer alphabetical system and reached for a letter at the far end to describe either the most serious or the least serious offense they had in mind. Whatever the source, the answer in Illinois is the same: there is no Class Z, and any charge, sentence, or penalty attributed to one is not real Illinois law.
If you’re trying to identify what a specific charge actually is, the controlling document is the charging instrument itself — the indictment or information filed by the prosecutor, which cites the statute and names the felony class. That citation will always point to Class M, X, 1, 2, 3, or 4.