diff --git a/core/libs/prx/libc/include/SonyCrt.hpp b/core/libs/prx/libc/include/SonyCrt.hpp
index 12500b15d1c..39a655f51e9 100644
--- a/core/libs/prx/libc/include/SonyCrt.hpp
+++ b/core/libs/prx/libc/include/SonyCrt.hpp
@@ -181,8 +181,7 @@ inline int SonyFltrounds(void) {
     }
 }
 
-inline unsigned __int128 SonyUdivti3(unsigned __int128 dividend, unsigned __int128 divisor) {
-    if (divisor == 0) throw std::runtime_error("__udivti3: integer divide by zero");
+inline unsigned __int128 SonyUdivmod128(unsigned __int128 dividend, unsigned __int128 divisor, unsigned __int128* remainderOut) {
     unsigned __int128 quotient = 0;
     unsigned __int128 remainder = 0;
     for (int i = 127; i >= 0; --i) {
@@ -192,9 +191,28 @@ inline unsigned __int128 SonyUdivti3(unsigned __int128 dividend, unsigned __int1
             quotient |= (unsigned __int128)1 << i;
         }
     }
+    *remainderOut = remainder;
     return quotient;
 }
 
+inline unsigned __int128 SonyUdivti3(unsigned __int128 dividend, unsigned __int128 divisor) {
+    if (divisor == 0) throw std::runtime_error("__udivti3: integer divide by zero");
+    unsigned __int128 remainder = 0;
+    return SonyUdivmod128(dividend, divisor, &remainder);
+}
+
+inline unsigned __int128 SonyUmodti3(unsigned __int128 dividend, unsigned __int128 divisor) {
+    if (divisor == 0) {
+        char message[96];
+        std::snprintf(message, sizeof(message), "__umodti3: integer divide by zero (0x%016llx%016llx %% 0)",
+            (unsigned long long)(dividend >> 64), (unsigned long long)dividend);
+        throw std::runtime_error(message);
+    }
+    unsigned __int128 remainder = 0;
+    SonyUdivmod128(dividend, divisor, &remainder);
+    return remainder;
+}
+
 inline __int128 SonyDivti3(__int128 dividend, __int128 divisor) {
     if (divisor == 0) throw std::runtime_error("__divti3: integer divide by zero");
     const bool negative = (dividend < 0) != (divisor < 0);
diff --git a/core/libs/prx/libc/src/RuntimeSupport.cpp b/core/libs/prx/libc/src/RuntimeSupport.cpp
index 0d83c1743d8..56a0f8d4993 100644
--- a/core/libs/prx/libc/src/RuntimeSupport.cpp
+++ b/core/libs/prx/libc/src/RuntimeSupport.cpp
@@ -188,4 +188,8 @@ unsigned __int128 APS5_VABI __udivti3_nid_postfix(unsigned __int128 dividend, un
     return SonyUdivti3(dividend, divisor);
 }
 
+unsigned __int128 APS5_VABI __umodti3_nid_postfix(unsigned __int128 dividend, unsigned __int128 divisor) {
+    return SonyUmodti3(dividend, divisor);
+}
+
 }
diff --git a/core/libs/tests/GuestCrt.cpp b/core/libs/tests/GuestCrt.cpp
index 4aeeabd1ea4..f6600788de1 100644
--- a/core/libs/tests/GuestCrt.cpp
+++ b/core/libs/tests/GuestCrt.cpp
@@ -32,6 +32,7 @@ char* APS5_VABI strtok_s_nid_postfix(char* str, const char* delim, char** contex
 int APS5_VABI __fpclassifyd_nid_postfix(double value);
 unsigned __int128 APS5_VABI __udivti3_nid_postfix(unsigned __int128 dividend, unsigned __int128 divisor);
 __int128 APS5_VABI __divti3_nid_postfix(__int128 dividend, __int128 divisor);
+unsigned __int128 APS5_VABI __umodti3_nid_postfix(unsigned __int128 dividend, unsigned __int128 divisor);
 SonyLconv* APS5_VABI localeconv_nid_postfix(void);
 int APS5_VABI sceAmprFpclassifyd(double value);
 unsigned int APS5_VABI _ZSt14_Random_devicev_nid_postfix();
@@ -109,6 +110,29 @@ int main() {
     }
     Require(trapped);
 
+    const unsigned __int128 unsignedMaximum = ~(unsigned __int128)0;
+    const unsigned __int128 largeDivisor = ((unsigned __int128)1 << 64) + 3;
+    Require(__umodti3_nid_postfix(100, 3) == 1);
+    Require(__umodti3_nid_postfix(0, 5) == 0);
+    Require(__umodti3_nid_postfix(3, 100) == 3);
+    Require(__umodti3_nid_postfix(unsignedMaximum, 1) == 0);
+    Require(__umodti3_nid_postfix(unsignedMaximum, unsignedMaximum) == 0);
+    Require(__umodti3_nid_postfix(largeDivisor, largeDivisor) == 0);
+    Require(__umodti3_nid_postfix(unsignedMaximum, 10) == 5);
+    Require(__umodti3_nid_postfix((unsigned __int128)1 << 100, 3) == 1);
+    Require(__umodti3_nid_postfix(unsignedMaximum, (unsigned __int128)1 << 64) == 0xFFFFFFFFFFFFFFFFull);
+    Require(__umodti3_nid_postfix(unsignedMaximum, largeDivisor) == 8);
+    Require(__umodti3_nid_postfix((unsigned __int128)1 << 127, largeDivisor) == 0x8000000000000006ull);
+    Require(__umodti3_nid_postfix(unsignedMaximum - 1, unsignedMaximum) == unsignedMaximum - 1);
+    Require(__umodti3_nid_postfix(unsignedMaximum, (unsigned __int128)1 << 127) == ((unsigned __int128)1 << 127) - 1);
+    trapped = false;
+    try {
+        __umodti3_nid_postfix(((unsigned __int128)0x1234 << 64) | 0x5678, 0);
+    } catch (const std::runtime_error& error) {
+        trapped = std::strcmp(error.what(), "__umodti3: integer divide by zero (0x00000000000012340000000000005678 % 0)") == 0;
+    }
+    Require(trapped);
+
     void* previous = sceAmprSetConstraintHandlerS(reinterpret_cast<void*>(&CountingHandler));
     Require(previous != nullptr);
     Require(previous != reinterpret_cast<void*>(&CountingHandler));
diff --git a/docs/dev/TechnicalDebt.md b/docs/dev/TechnicalDebt.md
index 41300fb18f5..6aa1e9e4f53 100644
--- a/docs/dev/TechnicalDebt.md
+++ b/docs/dev/TechnicalDebt.md
@@ -343,6 +343,7 @@ Throughout the project, every function at every stage either **does exactly what
 - [localeconv](../../core/libs/prx/libc/src/LocaleSupport.cpp) (libc, re-exported by libSceAmpr) - the 0x90-byte Dinkumware struct (empty monetary strings, `CHAR_MAX` for the 14 `char` fields, `decimal_point` ".", `_False`/`_True` "false"/"true") is read from the `libc.prx` that Astro's Playroom ships. It is a fixed C-locale table: whether the console changes it with `setlocale` is not known, and `_Frac_grouping`, `_Frac_sep`, `_No`, `_Yes` are empty strings as in that dump
 - [set_constraint_handler_s](../../core/libs/prx/libc/src/WideConversion.cpp) (libc, re-exported by libSceAmpr) - the default handler is assumed to abort; each module keeps its own handler state, so a handler set through one library is not seen by the other. `ctime_s` and `asctime_s` follow the Dinkumware 26-byte format with `EINVAL` for a buffer under 26 bytes, a null pointer or an out-of-range weekday/month; `ctime_s` uses the guest time zone of `localtime_s`, and the console's exact checks are not verified
 - [__udivti3](../../core/libs/prx/libc/src/RuntimeSupport.cpp) (libc, re-exported by libSceAmpr) - the hardware traps on a zero divisor; this throws instead
+- [__umodti3](../../core/libs/prx/libc/src/RuntimeSupport.cpp) (libc) - the hardware traps on a zero divisor; this throws instead
 - [AC1FtjqMCL0](../../core/libs/prx/libkernel/Unimplemented.cpp) (libkernel) - unknown name, signature
 - [0iEKNAvT600](../../core/libs/prx/libkernel/Unimplemented.cpp) (libkernel) - unknown name, signature
 - [2cELEBPdYQ0](../../core/libs/prx/libkernel/Unimplemented.cpp) (libkernel) - unknown name, signature