I recently read that a prenuptial agreement invalidates any marriage in the Catholic Church. Is that true?
No. The Catholic Church rejects any prenuptial agreement that contradicts the public declarations made in the Catholic Rite of Marriage (regardless of where the wedding took place or who officiated). A prenuptial agreement could not, for example: 1) sanction a genital relationship with someone other than the spouse in this agreement, 2) set a time limit for how long this marriage will last (five years, 12 years, etc.), or 3) rule out the possibility of children from this marriage.