Although it had been called Nagaoka-cho, Otokuni-gun before city status was granted, the city was named Nagaokakyo City because the city named 'Nagaoka City' already existed in Niigata Prefecture.
市制前は乙訓郡長岡町と呼ばれていたが、新潟県長岡市が先にあったので、このような名前となった。