iPhone 11 Pro Max compatible with Mojave?

The short answer is yes. Please refer to its System Requirements: iPhone 11 Pro Max - Technical Specifications

System Requirements 

• Apple ID (required for some features)
• Internet access
• Syncing to a Mac or PC requires: 
  • ...
  • macOS El Capitan 10.11.6 through macOS Mojave 10.14.6 using iTunes 12.8 or later

Reddasd Said:

"iPhone 11 Pro Max compatible with Mojave?: Hi there! Does anyone can tell me if iPhone 11 Pro Max and Mojave are compatible together? I have a MacBook Pro 2012 running with Mojave and I want to by a iPhone 11 Pro Max."

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Using Mojave on an iPhone:

If you are asking about installing Mojave on an iPhone, then short answer is "No". iPhone and Mac work on two completely different platforms, iOS and macOS, respectively.