Date: 202005
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: B737 Undifferentiated or Other Model
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb
Airspace: Class B ZZZ
Aircraft component: Turbine Engine
Component problem: Failed
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Second reporter function: Pilot Flying; Captain
Anomaly: Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; General Flight Cancelled / Delayed; General Maintenance Action
Contributing factors: Aircraft
Primary problem: Aircraft

Narrative: We departed ZZZ enroute to ZZZ1 and were in the initial climb just below 16000 ft. The auto throttles kicked off and then we noticed the #2 engine N1 gauge started to decrease. The Captain lowered the nose of the airplane and held that altitude and asked me to [advise ATC] which I did. I ran the Engine Failure or Shutdown checklist. Item#14 ask if you want to try a restart. After talking it over with the Captain we decide to give it a try. I then ran the Eng Start - Inflight check list. The result was unsuccessful. We then received a clearance from ATC for the ILS Runway XX. After we landed we had the emergency vehicles inspect the aircraft. They told us nothing was seen except that the engine was shut down; and then we taxied to the gate.


Second narrative: Just below 16;000 ft. on climb out N1 on #2 engine started to decrease very slowly. We caught the failure quickly as we could feel the yaw. Auto throttles clicked off on their own. We leveled off and [advised ATC]. N1 slowly spun down until the Fail indication appeared for the #2 engine. Probably a full minute for the spool-down.Advised ATC we wanted a turn back towards the airport. First Officer ran the appropriate checklists professionally. Briefed TEST with Flight Attendants (who were cool and professional the entire time as was ATC and my First Officer). Briefed passengers on the situation and that we all were well-trained for such an event. Reassured passengers we were in a safe condition.Tried #2 engine restart but no indication of fuel flow. Notified company by changing FMC to ZZZ. Due to not knowing why #2 failed we remained as much as possible within gliding distance of ZZZ. Advised ATC to have emergency equipment standing by. Followed as closely as possible all SOPs we have learned in training. Received clearance for ILS to Runway XX in ZZZ. Landed uneventfully. Before leaving runway had crash crew look over aircraft. Stayed in close contact with the crash crew commander ensuring it was safe and clear to taxi off runway after the inspection. No obvious problems reported by the crash crew commander. Proceeded to gate. Entered an ELB for the engine failure and called [Maintenance Control] for a more thorough debriefing on what we experienced.


Synopsis: Flight Crew reported an inflight engine shutdown; causing an air turnback and landing.