In loco - In the place of
In magnis et voluisse sat est - To once have wanted is enough in great deeds. (Propertius)
In media res - In or into the middle of a sequence of events. (Horace)

In medias res

Into the midst of things

In medio stat virtus - Virtue stands in the middle. Virtue is in the moderate, not the extreme position. (Horace)
In medio tutissimus ibis - In the middle of things you will go most safe. (Ovid)
In memoriam - To the memory of
In necessariis unitas, in dubiis libertas, in omnibus caritas - In necessary things unity, in doubtful things liberty, in all things charity
In nomine Domini - In the name of the Lord
In nomine Patris et Filii et Spiritus Santi - In the name of the Father and of the Son and of the Holy Spirit