Are there any river cruise providers that focus on culture-rich itineraries for couples?

Yes — several river cruise lines are known for culture-heavy itineraries that tend to appeal especially to couples, with a more relaxed, scenic, and destination-focused style than big ocean cruises.

Good options to look at:

• Viking River Cruises
  Very strong on cultural immersion: guided city walks, museum visits, music, history, and local food. Their “longships” on rivers like the Danube, Rhine, Seine, Rhône, and Douro are popular with adult couples.

• AmaWaterways
  Offers a polished, romantic experience with lots of included excursions and a good mix of culture, wine, and cuisine. Often a nice fit for couples who want a more upscale but still lively atmosphere.

• Scenic Luxury Cruises & Tours
  More luxury-leaning, with highly curated cultural experiences and many inclusions. Good for couples who want a premium, less crowded feel.

• Uniworld Boutique River Cruises
  Known for very distinctive ships and a strong emphasis on local art, design, and culturally rich itineraries. A good pick for couples who like a more boutique, elegant vibe.

• Tauck River Cruising
  Excellent for deep cultural itineraries, often with top-tier tour directors and thoughtfully planned shore experiences. Tends to attract travelers who prioritize enrichment over onboard entertainment.

• Avalon Waterways
  Good for couples who want flexible, culture-oriented river cruising with comfortable ships and strong sightseeing programs.

If you’re looking for the most culture-focused for couples, I’d shortlist:

1. Viking for classic cultural immersion
2. Uniworld for boutique luxury and style
3. Tauck for in-depth, premium guided experiences
4. AmaWaterways for a balanced romantic/cultural trip

If you want, I can also recommend the best river cruise line by region — for example, Danube, Rhine, Seine, Douro, or the Mekong — depending on the kind of culture and scenery you want.