A fluid line coupling includes a receiving part and a locking part connectable to the receiving part. The locking part includes a plurality of elastically resilient spring tongues engageable behind an annular collar formed on a plug-in part that is insertable into the receiving part. A securing part includes a plurality of elongate securing arms. Guide elements are formed on the securing part and the receiving part that are engagable with one another to displace the securing part in relation to the receiving part. In a securing position of the securing part, each securing arm bears against a respective associated spring tongue and prevents the spring tongue from deflecting outwardly. In this manner, the plug-in part is secured by a very high pull-out force against being pulled out of the receiving part.