A male luer connector includes a body having a first end configured to be connected to a fluid line, a second end opposed to the first end, and a body longitudinal axis. The second end is configured to be inserted into and form a luer slip connection with a female luer connector. The male luer connector also includes a locking collar that is connected to the body in a manner such that the locking collar rotates about the longitudinal axis. In some cases, the body second end does not protrude beyond a plane that is transverse to the longitudinal axis and that includes an end face of the locking collar, and/or when male and female connectors are engaged, the locking collar engages an outer surface of the female fluid line connector and is deformed by the engagement.