Waddlia is a genus of bacteria in its own family, Waddliaceae. Species in this genus have a Chlamydia-like cycle of replication and their ribosomal RNA genes are 80–90% identical to ribosomal genes in the Chlamydiaceae.

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The type species is Waddlia chondrophila strain WSU 86-1044T, which was isolated from the tissues of a first-trimester aborted bovine fetus. Isolated in 1986, this species was originally characterized as a Rickettsia. DNA sequencing of the ribosomal genes corrected the characterization. Another W. chondrophila strain, 2032/99, was found along with Neospora caninum in a septic stillborn calf.

Waddlia chondrophila may be linked to miscarriages in pregnant women. A study found Waddlia chondrophila present in the placenta and vagina of 32 women, 10 of which who had miscarriages.^[3] It is hypothesized that the bacterial grows in placental cells, damaging the placenta.^[4]

The species Waddlia malaysiensis G817 has been proposed. W. malaysiensis was identified in the urine of Malaysian fruit bats (Eonycteris spelaea).

• List of bacterial orders
• List of bacteria genera