What assets are untouchable in a divorce?
What you owned before the marriage, what you inherited, and what was given to you individually is generally separate property and is not divided. (A prenup can redraw these lines, where one exists and holds up.) Everything acquired during the marriage generally is, whatever name is on it.
The trap is not the rule. It is how easily separate property becomes marital without anyone intending it.
The basic split
Marital property is generally what was acquired during the marriage. Whose name is on the account or the title usually does not decide it. A salary earned during the marriage is marital even though it landed in one person's account, and a car in one name bought with joint money is still marital.
Separate property is generally what you brought into the marriage, what you inherited at any point, what was gifted to you specifically rather than to the couple, and in many states certain personal injury awards.
That is the shape of it in both community property and equitable distribution states. Which system your state uses mostly changes how the marital pool gets divided rather than what falls into it. A handful of states are the exception and put everything in the divisible pot regardless of where it came from. Washington, Indiana, Massachusetts, Connecticut, New Hampshire and Vermont are the usual examples, and that is not a closed list. So do not read your state's absence from it as a guarantee. Ask what your state does before you count anything as untouchable.
How separate property stops being separate
Three ways, and the first is by far the most common.
Commingling. You inherit money and deposit it into a joint account. You use it for a shared house. It gets mixed with marital funds until it cannot be told apart. Once separate money is blended into marital money, it can lose its character entirely, and the more thoroughly it was mixed the harder it is to claw back.
Adding your spouse's name. Retitling a premarital house into both names, or adding a spouse to an account, is treated in some states as converting it or as a gift to the marriage, but not everywhere. California, for one, requires an express written declaration before separate property is converted at all, and gives you a right of reimbursement for separate money you put into a jointly owned asset. Whether retitling actually cost you anything is a state-law question with a real answer, so get it before you concede the point.
Marital effort increasing its value. If you owned a business or a property before the marriage and it grew because you worked on it during the marriage, the increase may be marital even though the original asset is not. Growth that happened passively, like an untouched investment rising with the market, is treated differently from growth you produced.
The burden falls on you
The person claiming something is separate generally has to prove it, and proof means records: statements showing what the account held on the wedding day, the inheritance paperwork, the deed, the trail showing the money stayed apart.
This is why people lose separate property claims they were genuinely entitled to. Not because the rule failed them, because ten years later nobody could show where the money went.
If you have separate property you care about, find the documents now, while they are findable.
The questions people actually ask
Are separate bank accounts safe? Not by themselves. An account in your sole name holding income you earned during the marriage is still marital. The account's name is not what determines its character; where the money came from is.
Is my inheritance protected? Generally yes, if you kept it separate and can prove it. Frequently no, once it has been through a joint account or spent on the family home.
What about a gift from my parents? Depends on who it was given to. A gift to you is separate; a gift to the two of you is not, and cards and notes have decided this more than once.
Is my retirement mine because it is in my name? No. The portion that accrued during the marriage is generally marital, whoever the account belongs to.
What not to do about it
Do not move separate money around now to make it look more separate. Transfers during or shortly before a divorce get examined closely, and an explanation that sounds like protection reads to a court like concealment. Full disclosure is required of both of you regardless, and being the person whose disclosure was clean is worth more than anything hiding could preserve.
If you want to protect something, the tool is documentation, not relocation.
What counts as separate property, how commingling is treated, and whether appreciation is divided all vary by state, and this area has more state-to-state variation than almost any other. If you have significant separate property, that is worth a licensed family-law attorney before you agree to anything.