In the shocking wake of JOAN RIVERS’ death, the fate of “E!” smash-hit “Fashion Police” is suddenly up in the air – and now a bitter battle’s brewing between Joan’s co-host/pal GIULIANA RANCIC and ex-“Extra” hottie MARIA MENOUNOS, freshly signed to a multi-year deal to (1) star in her own “Untold with Maria Menounos” show, plus (2) appear on “Live From E!” and network specials!

Said a source: “Giuliana and Maria are suddenly at war over who’s the network’s top newsdog! It’s a showdown – and getting uglier by the second! Giuliana, upset when she first discovered ‘E!’ was even negotiating to hire Maria, turned livid when execs signed the younger star (36) to a multi-year deal that includes both talent and production roles – even though Giuliana (40) had just signed to stay until early 2016. She now fears they’re grooming Maria to replace her when her contract runs out. Joan’s death could not have come at a worse time for Giuliana! Joan would have protected her no matter what.”

But now Giuliana’s facing the wolves alone – and it gets worse: RYAN SEACREST, her longtime red carpet co-host/“E!” news co-anchor is NOT taking her side in the battle.

Said an insider: “Ryan’s good friends with Maria, so he’s staying out of it … and Giuliana suspects Ryan may have even helped Maria land her sweet deal! But despite being distraught over Joan’s sudden death – and what she feels is an ‘E!’ slap in the face – Giuliana isn’t about to run away with her tail between her legs. After fighting through her recent cancer ordeal, she believes she can overcome anything – even the cute new kid in town!” Stay tuned.