This is a revised version of an article that I originally wrote for the Island Register.
Along with marriage dispensations, the age of majority is another piece of information from Catholic marriage records that is useful to genealogists.
In general, the age of majority was 18 for females and 21 for males. However, the exact usage could vary by priest or diocese.
If one or both of the parties was under the age of majority, the priest required their parent's permission before he could perform the marriage ceremony. Thus many (although not all) of the Catholic marriage records will note whether or not the bride and groom had reached the age of majority. This might be written as "son/daughter of (not of) age", "major (or minor) son/daughter", or, in the case of French records "fils (or fille) majeur(e)/mineur(e)".
If both parties were over the age of majority only the consent of the bride and groom was required - parental permission was not necessary.
Obviously, we can use this notation to get a rough estimate of a person's age. If a woman was married in 1818 and she was under the age of majority (under 18), she had to have been born circa 1800 or later. Conversely, if she was over the age of majority, she had to have been born circa 1800 or earlier.
While useful, the accuracy of the information depended on the couple giving the priest their actual ages. This didn't always happen, and there might not have been a way for the priest to know it.
When the Catholic marriage records are complete they can provide a lot more useful information than just names and dates. Along with the dispensations (giving clues into lineage and relationships) and the ages of majority (giving clues to age), marriage records often include: the names of parents, place of residence and/or place of origin, occupation, and, in some instances, the relationship of the marriage witnesses to the bride and groom. Unfortunately, these supplementary facts are sometimes overlooked by researchers or excluded from transcripts, indices, and finding aids. It's always best to look at the original documents whenever possible and to record all of the information they contain, not just the names and dates.
Please note that the age of majority isn't always cut and dry. For example, I believe that some Irish priests used 25 as the age of majority for both males and females, rather than 21 and 18 as noted above. Further, there are some records where parental permission was granted even though both the bride and the groom were over the age of majority and, conversely, there are some records that lack parental permission even though one or both of the parties was a minor.
I don't claim to be an expert on this matter but I do hope that the information I have provided will prove useful to others in their research.