Can I apply for a green card if I came here on a visitor visa and overstayed?

If you marry a U.S. citizen, you can usually still adjust status (get a green card) inside the U.S., even if you overstayed.

If your petitioner is a green card holder (not a citizen), your overstay might make you ineligible for adjustment of status unless you leave and re-enter legally (which can trigger bans).

If you are married to a U.S. citizen, you may file Form I-130 and Form I-485 together (concurrent filing), even after overstaying.

Overstaying a visa can complicate employment or travel, so it's best to apply for adjustment of status as soon as you qualify.