diff --git a/app/models.py b/app/models.py
new file mode 100644
index 0000000..7889635
--- /dev/null
+++ b/app/models.py
@@ -0,0 +1,68 @@
+from datetime import datetime, timezone
+from enum import StrEnum
+from typing import Self
+from uuid import UUID
+
+from pydantic import BaseModel, ConfigDict, Field, HttpUrl, model_validator
+
+
+class State(StrEnum):
+    UNKNOWN = "unknown"
+    UP = "up"
+    DOWN = "down"
+    ERROR = "error"
+
+
+class CurrentStatus(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+    state: State = State.UNKNOWN
+    checked_at: datetime | None = None
+    latency_ms: float | None = Field(default=None, ge=0)
+    http_status: int | None = Field(default=None, ge=100, le=599)
+    final_url: str | None = None
+    error: str | None = None
+
+
+class MonitorCreate(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+    name: str = Field(min_length=1, max_length=120)
+    url: HttpUrl
+
+    @model_validator(mode="after")
+    def safe_url_shape(self) -> Self:
+        if self.url.scheme not in {"http", "https"}:
+            raise ValueError("only http and https URLs are supported")
+        if self.url.username is not None or self.url.password is not None:
+            raise ValueError("URL credentials are not allowed")
+        return self
+
+
+class MonitorUpdate(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+    name: str | None = Field(default=None, min_length=1, max_length=120)
+    url: HttpUrl | None = None
+
+    @model_validator(mode="after")
+    def validate_update(self) -> Self:
+        if self.name is None and self.url is None:
+            raise ValueError("at least one field is required")
+        if self.url is not None:
+            if self.url.scheme not in {"http", "https"}:
+                raise ValueError("only http and https URLs are supported")
+            if self.url.username is not None or self.url.password is not None:
+                raise ValueError("URL credentials are not allowed")
+        return self
+
+
+class Monitor(BaseModel):
+    model_config = ConfigDict(extra="forbid")
+    id: UUID
+    name: str
+    url: HttpUrl
+    created_at: datetime
+    updated_at: datetime
+    current_status: CurrentStatus
+
+
+def utcnow() -> datetime:
+    return datetime.now(timezone.utc)