Short answer: National Lampoon’s Christmas Vacation is available to stream on Max in the U.S. You can also rent or buy it on several platforms (Apple TV, Google Play, YouTube, Vudu, Amazon Video, Sky Store, etc.), and some regions have options on Now TV/Sky platforms or Crave/Stan depending on country. Details and up-to-date options

• United States
  • Streaming: Max (formerly HBO Max) currently carries National Lampoon’s Christmas Vacation for subscribers in the U.S. Ad-free plans or with ads may apply depending on your tier. [web results imply Max availability in the U.S.]
  • Rentals/ purchases: Available to rent or buy on Apple TV, Google Play, YouTube, Vudu, and other major digital storefronts. [web results indicate common availability across platforms]
• Other regions
  • Canada: Crave sometimes carries the film; streaming and purchase options may vary by catalog season. [web results indicate Crave as a streaming option]
  • Australia: Now TV Cinema, Stan, Foxtel Now, and Binge are listed streaming options in some guides; some services may require paid subscriptions or trials. [web results show these regional options]
  • United Kingdom / Europe: JustWatch shows options like Sky Go, Now TV Cinema, and rental/purchase on Apple TV, Rakuten TV, Amazon Video, Sky Store, etc. Availability can change by region. [web results indicate these services]
• Netflix: Not typically available on Netflix in most regions; availability varies by country and time. If it’s not in your local library, you may find it on Max or other platforms instead. [web results note Netflix absence in certain regions]

What to check right now

• If you’re in the U.S.: Open Max and search for Christmas Vacation to confirm streaming availability and current pricing for your plan.
• If you prefer to rent/buy: Check Apple TV, Google Play, YouTube, Vudu, Amazon Video, or Sky Store for your country to compare price and format (HD/4K).
• If you’re traveling or in a different country: Look up your local streaming services or digital stores (JustWatch or a local equivalent) to see current availability, since catalogs change over time.

If you’d like, specify your country and whether you prefer streaming vs. rental/purchase, and I can tailor the exact current options and steps to watch.