B787 captain reported an near midair collision approaching the final approach fix at den.

Attributes
ACN	1654321
Time
Date	201906
Local Time Of Day	0601-1200
Place
Locale Reference	D01.TRACON
State Reference	CO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B787 Dreamliner Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach Final Approach
Flight Plan	IFR
Aircraft 2
Make Model Name	B737 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Initial Approach
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 118 Flight Crew Total 16865 Flight Crew Type 118
Events
Anomaly	ATC Issue All Types Conflict NMAC Deviation - Procedural Published Material / Policy
Miss Distance	Horizontal 500 Vertical 200

Narrative:

We were cleared for the approach to fly the ILS 16R procedure. Near the meryn intersection approach called out traffic on a dog leg to 16L. We were very busy at this point in the approach and I stated to the pm I had traffic behind us approaching 16L which was the logical but wrong assumption. A very short time later we get an immediate and simultaneous TA and RA which I responded to staying within the advisory bars and then noticed; incredulously; a 737 passing on my immediate left estimating less than 500 ft horizontally and 200 ft below us on a southeasterly heading turning towards 16L.to be honest I was shocked at not only the controller putting an aircraft underneath us to runway 16L but I cannot believe [that] aircraft Y was in the class B airspace at his altitude and at our position to the runway. Further and to put it bluntly it was a foolish and unsafe maneuver by the crew [of] aircraft Y to fly underneath us at that altitude to maneuver for 16L. Let alone accept a clearance to do so.finally if we were spaced the same distance to the runways; why didn't we get 16L (we were coming off the kipper 5) with aircraft Y coming from the west 16R? This sequencing made zero sense.quite frankly the potential for a collision was high confirmed by the fact getting an RA that close to the FAF. I called the TRACON supervisor upon arrival and explained my concern. He took my number and promised a call back after reviewing the incident. I did not catch aircraft Y's flight number.

Original NASA ASRS Text

Title: B787 Captain reported an NMAC approaching the final approach fix at DEN.

Narrative: We were cleared for the approach to fly the ILS 16R procedure. Near the MERYN intersection approach called out traffic on a dog leg to 16L. We were very busy at this point in the approach and I stated to the PM I had traffic behind us approaching 16L which was the logical but wrong assumption. A very short time later we get an immediate and simultaneous TA and RA which I responded to staying within the advisory bars and then noticed; incredulously; a 737 passing on my immediate left estimating less than 500 ft horizontally and 200 ft below us on a southeasterly heading turning towards 16L.To be honest I was shocked at not only the controller putting an aircraft underneath us to runway 16L but I cannot believe [that] Aircraft Y was in the Class B airspace at his altitude and at our position to the runway. Further and to put it bluntly it was a foolish and unsafe maneuver by the crew [of] Aircraft Y to fly underneath us at that altitude to maneuver for 16L. Let alone accept a clearance to do so.Finally if we were spaced the same distance to the runways; why didn't we get 16L (we were coming off the Kipper 5) with Aircraft Y coming from the west 16R? This sequencing made zero sense.Quite frankly the potential for a collision was high confirmed by the fact getting an RA that close to the FAF. I called the TRACON Supervisor upon arrival and explained my concern. He took my number and promised a call back after reviewing the incident. I did not catch Aircraft Y's flight number.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.