A false friend is a word in another language that looks or sounds like an English word but means something different, sometimes very different. Spanish and English share an enormous amount of vocabulary through Latin, which makes reading Spanish genuinely easier for English speakers than most other languages, but that same shared vocabulary is exactly where the false friends live. A handful of them are common enough in real writing and real conversation that they're worth learning deliberately, starting with the one that causes the most real embarrassment.
The one everyone should know first: embarazada
Embarazada means pregnant, not embarrassed. If you're trying to say you're embarrassed about something, the word you want is avergonzada (or avergonzado). This particular mix-up happens often enough between English and Spanish speakers that most Spanish teachers mention it in the first few weeks of a course, and it's exactly the kind of word that, if you never learned it deliberately, you might guess wrong the one time it actually matters.
The rest of the working list
Éxito means success, not exit. A headline about a company's éxito is celebrating an achievement, not describing a doorway. The word for exit is salida.
Actualmente means currently or nowadays, not actually. "Actualmente vive en Madrid" means "She currently lives in Madrid," not a correction of a previous statement. Actually, in the sense of "in fact," is en realidad.
Carpeta means folder, the kind you keep papers in, not carpet. Carpet, the flooring, is alfombra.
Sopa means soup, not soap. Soap, the thing you wash with, is jabón. These two are close enough in spelling that mixing them up in a grocery list is a common beginner mistake.
Red means net or network, most often used for the internet ("la red") or a sports net, not the color. The color red is rojo.
Sensible means sensitive, easily affected emotionally or physically, not sensible in the English sense of reasonable or practical. Reasonable, in that sense, is sensato.
Largo means long, referring to length or duration, not large in the sense of big overall. Large, meaning big, is grande. A largo día is a long day, not a big one.
Asistir means to attend, most commonly used for attending a class, meeting, or event, not to assist or help. "Asistí a la reunión" means "I attended the meeting." To assist or help is ayudar.
Pie means foot, the body part, not the dessert. The dessert is pastel or tarta, depending on the country and the kind.
Lectura means reading, the activity or a piece of reading material, not a lecture. A university lecture is una conferencia or una clase, depending on the setting. This one matters specifically if you're reading about education or literacy, where lectura shows up constantly and never means what an English speaker's first guess would be.
Three more that show up constantly in real writing
Molestar means to bother or annoy, not to molest in the English sense. "Perdón, no quería molestarte" means "Sorry, I didn't mean to bother you." This one is worth learning deliberately precisely because the English meaning is so much more serious than the Spanish one, and a nervous mistranslation in either direction is worse than most false friends on this list.
Recordar means to remember, not to record. "No recuerdo su nombre" means "I don't remember his name." To record something, audio or video, is grabar.
Realizar means to carry out or achieve, not to realize in the sense of suddenly understanding. "La empresa realizó el proyecto" means "The company carried out the project." To realize, as in understanding something, is darse cuenta.
A worked example: one sentence, three traps
Take a sentence you might actually read in Spanish news: "El actor se sintió avergonzado después de que un periodista intentara molestarlo con preguntas sobre su vida personal, pero al final no recordaba haber dicho nada malo." Read with the English-shaped guess, "molestarlo" looks alarming and "recordaba" might get skipped as unfamiliar. Read correctly, it means: "The actor felt embarrassed after a journalist tried to bother him with questions about his personal life, but in the end he didn't remember having said anything wrong." Every word in that sentence is ordinary Spanish. It only reads as strange if two or three false friends are doing damage at once, which is exactly how they show up in real text, not one at a time in a vocabulary list.
Catching them without studying the list first
Memorizing this list top to bottom before you start reading isn't necessary, and it isn't really how these words get learned anyway. Most people catch their first two or three false friends by tripping over them in a real sentence, not by drilling a table. What's worth building instead is the reflex: a sentence made entirely of words you recognize shouldn't still feel confusing. When that happens, the fluent-sounding, familiar word is the more likely culprit than a grammar point you missed, so try swapping in the real Spanish meaning before assuming you've hit something genuinely advanced. The ones actually worth writing down are whichever two or three from this page you personally misread first. That short, personal list does more work than the full one above, because it's built from mistakes you've actually made rather than ones you might make.
Why English speakers specifically get these wrong
Most of these pairs share a real Latin root with their English look-alikes, which is exactly what makes the mistake so tempting: the words aren't randomly similar, they're historically related, and the meaning simply drifted apart in one language while staying put in the other. Éxito and English "exit" both come from the Latin exitus, meaning "a going out" or "an outcome." English kept the literal sense of leaving; Spanish kept the more abstract sense of an outcome, and specifically a good one. Knowing the shared root doesn't stop you from misreading the word the first few times you meet it, but it does explain why these particular words survive as traps instead of just fading into the large pile of Spanish-English vocabulary that lines up cleanly.
Reading past them
The same signal works here as with any false friend: if a familiar-looking word makes the sentence around it stop making sense, the word is usually the problem, not your reading. A sentence claiming someone is "muy sensible" after receiving difficult news reads as strange if you assume it means sensible in the practical sense, and reads exactly right once you know it means emotionally sensitive. A short list like the one above, reviewed occasionally while you're actually reading real Spanish text rather than memorized once in isolation, is what makes these words stop being traps.