Cessna 177 pilot reported an engine malfunction during cruise in VMC conditions. The pilot diverted to the closest airport and landed safely.

Narrative

Approximately 12nm north-east of ZZZ; I noticed that my oil pressure gauges showed that the oil pressure dropped to the lower redline; while cruising westbound at 2500 ft.As both the instrument gauge as well as the engine monitor agreed about the low oil pressure; while at this point both oil and cylinder head temperatures were normal; I decided to divert to the closest airport; ZZZ; while reducing engine power to the minimum reasonable power setting to keep altitude and safe airspeed.At this point; I couldn't notice anything other than the indications being wrong.I requested priority for landing at the pilot-controlled airfield due to the oil pressure issue.After landing safely; I checked the oil level in the engine sump and found that almost all the oil was gone. I did notice that my left landing gear and landing gear strut were covered in oil.I also noticed a large junk being broken off the spinner bulkhead; which may have caused the oil leak (it has not been investigated by my A&P at this point)Before flying this day; I did check the engine oil level and filled it to 7qt; meaning; this was likely a sudden loss of oil.