Thelaziidae is a family of spirurian nematodes, which form the mid-sized lineage of the superfamily Thelazioidea. Like all nematodes, they have neither a circulatory nor a respiratory system.

They number 7 genera or so, with a few dozen species all together. Mostly parasites of birds, a few have also been found in other vertebrates.^[1]

The subfamily Oxyspirurinae is monotypic, as are several little-known genera in the Thelaziinae; these all might not be valid. All together, the systematic layout of this family is liable to change and cannot be considered more than tentative.^[1]

Subfamily Oxyspirurinae Skrjabin, 1916

• Oxyspirura Dräsche in Stossich, 1897

Subfamily Thelaziinae Skrjabin, 1915

• Ceratospira Schneider, 1866
• Hempelia Vaz, 1937
• Pancreatonema McVicar & Gibson, 1975
• Pericyema Railliet, 1925
• Thelazia Bosc in Blainville, 1819
• Thylaconema Chandler, 1929