Dexter1 “Dexter” is on a premiere spree.

The fifth season premiere of Showtime’s “Dexter” averaged 1.8 million viewers on Sunday in its 9 p.m. time slot, up 16% from last year’s premiere (1.5 million).

For Showtime, that reps both “Dexter’s” best premiere ever, as well as the biggest season premiere for a Showtime series in 15 years. (Strangely, that was the March 1995 preem of “Outer Limits” — go figure!)

A second showing of “Dexter” at 11 p.m. averaged 575,000 viewers. Assuming there’s not much duplication, that comes out to around 2.3 million viewers for the evening (up 22% from last year’s 1.9 million premiere night audience).

Here’s a ratings track of “Dexter’s” five season premieres: